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1 <!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
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2
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3 <chapter id="chap.mq">
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4 <?dbhtml filename="managing-change-with-mercurial-queues.html"?>
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5 <title>Managing change with Mercurial Queues</title>
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6
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7 <sect1 id="sec.mq.patch-mgmt">
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8 <title>The patch management problem</title>
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9
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10 <para>Here is a common scenario: you need to install a software
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11 package from source, but you find a bug that you must fix in the
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12 source before you can start using the package. You make your
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13 changes, forget about the package for a while, and a few months
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14 later you need to upgrade to a newer version of the package. If
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15 the newer version of the package still has the bug, you must
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16 extract your fix from the older source tree and apply it against
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17 the newer version. This is a tedious task, and it's easy to
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18 make mistakes.</para>
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19
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20 <para>This is a simple case of the <quote>patch management</quote>
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21 problem. You have an <quote>upstream</quote> source tree that
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22 you can't change; you need to make some local changes on top of
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23 the upstream tree; and you'd like to be able to keep those
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24 changes separate, so that you can apply them to newer versions
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25 of the upstream source.</para>
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26
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27 <para>The patch management problem arises in many situations.
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28 Probably the most visible is that a user of an open source
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29 software project will contribute a bug fix or new feature to the
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30 project's maintainers in the form of a patch.</para>
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31
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32 <para>Distributors of operating systems that include open source
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33 software often need to make changes to the packages they
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34 distribute so that they will build properly in their
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35 environments.</para>
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36
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37 <para>When you have few changes to maintain, it is easy to manage
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38 a single patch using the standard <command>diff</command> and
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39 <command>patch</command> programs (see section <xref
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40 linkend="sec.mq.patch"/> for a discussion of these
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41 tools). Once the number of changes grows, it starts to make
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42 sense to maintain patches as discrete <quote>chunks of
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43 work,</quote> so that for example a single patch will contain
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44 only one bug fix (the patch might modify several files, but it's
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45 doing <quote>only one thing</quote>), and you may have a number
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46 of such patches for different bugs you need fixed and local
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47 changes you require. In this situation, if you submit a bug fix
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48 patch to the upstream maintainers of a package and they include
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49 your fix in a subsequent release, you can simply drop that
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50 single patch when you're updating to the newer release.</para>
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51
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52 <para>Maintaining a single patch against an upstream tree is a
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53 little tedious and error-prone, but not difficult. However, the
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54 complexity of the problem grows rapidly as the number of patches
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55 you have to maintain increases. With more than a tiny number of
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56 patches in hand, understanding which ones you have applied and
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57 maintaining them moves from messy to overwhelming.</para>
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58
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59 <para>Fortunately, Mercurial includes a powerful extension,
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60 Mercurial Queues (or simply <quote>MQ</quote>), that massively
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61 simplifies the patch management problem.</para>
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62
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63 </sect1>
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64 <sect1 id="sec.mq.history">
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65 <title>The prehistory of Mercurial Queues</title>
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66
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67 <para>During the late 1990s, several Linux kernel developers
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68 started to maintain <quote>patch series</quote> that modified
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69 the behaviour of the Linux kernel. Some of these series were
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70 focused on stability, some on feature coverage, and others were
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71 more speculative.</para>
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72
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73 <para>The sizes of these patch series grew rapidly. In 2002,
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74 Andrew Morton published some shell scripts he had been using to
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75 automate the task of managing his patch queues. Andrew was
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76 successfully using these scripts to manage hundreds (sometimes
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77 thousands) of patches on top of the Linux kernel.</para>
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78
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79 <sect2 id="sec.mq.quilt">
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80 <title>A patchwork quilt</title>
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81
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82 <para>In early 2003, Andreas Gruenbacher and Martin Quinson
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83 borrowed the approach of Andrew's scripts and published a tool
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84 called <quote>patchwork quilt</quote>
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85 <citation>web:quilt</citation>, or simply <quote>quilt</quote>
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86 (see <citation>gruenbacher:2005</citation> for a paper
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87 describing it). Because quilt substantially automated patch
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88 management, it rapidly gained a large following among open
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89 source software developers.</para>
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90
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91 <para>Quilt manages a <emphasis>stack of patches</emphasis> on
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92 top of a directory tree. To begin, you tell quilt to manage a
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93 directory tree, and tell it which files you want to manage; it
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94 stores away the names and contents of those files. To fix a
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95 bug, you create a new patch (using a single command), edit the
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96 files you need to fix, then <quote>refresh</quote> the
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97 patch.</para>
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98
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99 <para>The refresh step causes quilt to scan the directory tree;
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100 it updates the patch with all of the changes you have made.
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101 You can create another patch on top of the first, which will
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102 track the changes required to modify the tree from <quote>tree
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103 with one patch applied</quote> to <quote>tree with two
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104 patches applied</quote>.</para>
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105
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106 <para>You can <emphasis>change</emphasis> which patches are
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107 applied to the tree. If you <quote>pop</quote> a patch, the
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108 changes made by that patch will vanish from the directory
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109 tree. Quilt remembers which patches you have popped, though,
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110 so you can <quote>push</quote> a popped patch again, and the
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111 directory tree will be restored to contain the modifications
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112 in the patch. Most importantly, you can run the
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113 <quote>refresh</quote> command at any time, and the topmost
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114 applied patch will be updated. This means that you can, at
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115 any time, change both which patches are applied and what
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116 modifications those patches make.</para>
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117
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118 <para>Quilt knows nothing about revision control tools, so it
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119 works equally well on top of an unpacked tarball or a
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120 Subversion working copy.</para>
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121
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122 </sect2>
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123 <sect2 id="sec.mq.quilt-mq">
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124 <title>From patchwork quilt to Mercurial Queues</title>
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125
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126 <para>In mid-2005, Chris Mason took the features of quilt and
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127 wrote an extension that he called Mercurial Queues, which
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128 added quilt-like behaviour to Mercurial.</para>
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129
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130 <para>The key difference between quilt and MQ is that quilt
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131 knows nothing about revision control systems, while MQ is
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132 <emphasis>integrated</emphasis> into Mercurial. Each patch
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133 that you push is represented as a Mercurial changeset. Pop a
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134 patch, and the changeset goes away.</para>
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135
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136 <para>Because quilt does not care about revision control tools,
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137 it is still a tremendously useful piece of software to know
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138 about for situations where you cannot use Mercurial and
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139 MQ.</para>
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140
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141 </sect2>
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142 </sect1>
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143 <sect1>
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144 <title>The huge advantage of MQ</title>
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145
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146 <para>I cannot overstate the value that MQ offers through the
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147 unification of patches and revision control.</para>
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148
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149 <para>A major reason that patches have persisted in the free
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150 software and open source world&emdash;in spite of the
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151 availability of increasingly capable revision control tools over
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152 the years&emdash;is the <emphasis>agility</emphasis> they
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153 offer.</para>
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154
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155 <para>Traditional revision control tools make a permanent,
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156 irreversible record of everything that you do. While this has
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157 great value, it's also somewhat stifling. If you want to
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158 perform a wild-eyed experiment, you have to be careful in how
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159 you go about it, or you risk leaving unneeded&emdash;or worse,
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160 misleading or destabilising&emdash;traces of your missteps and
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161 errors in the permanent revision record.</para>
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162
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163 <para>By contrast, MQ's marriage of distributed revision control
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164 with patches makes it much easier to isolate your work. Your
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165 patches live on top of normal revision history, and you can make
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166 them disappear or reappear at will. If you don't like a patch,
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167 you can drop it. If a patch isn't quite as you want it to be,
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168 simply fix it&emdash;as many times as you need to, until you
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169 have refined it into the form you desire.</para>
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170
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171 <para>As an example, the integration of patches with revision
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172 control makes understanding patches and debugging their
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173 effects&emdash;and their interplay with the code they're based
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174 on&emdash;<emphasis>enormously</emphasis> easier. Since every
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175 applied patch has an associated changeset, you can give <command
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176 role="hg-cmd">hg log</command> a file name to see which
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177 changesets and patches affected the file. You can use the
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178 <command role="hg-cmd">hg bisect</command> command to
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179 binary-search through all changesets and applied patches to see
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180 where a bug got introduced or fixed. You can use the <command
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181 role="hg-cmd">hg annotate</command> command to see which
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182 changeset or patch modified a particular line of a source file.
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183 And so on.</para>
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184
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185 </sect1>
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186 <sect1 id="sec.mq.patch">
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187 <title>Understanding patches</title>
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188
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189 <para>Because MQ doesn't hide its patch-oriented nature, it is
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190 helpful to understand what patches are, and a little about the
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191 tools that work with them.</para>
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192
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193 <para>The traditional Unix <command>diff</command> command
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194 compares two files, and prints a list of differences between
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195 them. The <command>patch</command> command understands these
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196 differences as <emphasis>modifications</emphasis> to make to a
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197 file. Take a look below for a simple example of these commands
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198 in action.</para>
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199
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200 &interaction.mq.dodiff.diff;
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201
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202 <para>The type of file that <command>diff</command> generates (and
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203 <command>patch</command> takes as input) is called a
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204 <quote>patch</quote> or a <quote>diff</quote>; there is no
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205 difference between a patch and a diff. (We'll use the term
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206 <quote>patch</quote>, since it's more commonly used.)</para>
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207
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208 <para>A patch file can start with arbitrary text; the
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209 <command>patch</command> command ignores this text, but MQ uses
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210 it as the commit message when creating changesets. To find the
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211 beginning of the patch content, <command>patch</command>
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212 searches for the first line that starts with the string
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213 <quote><literal>diff -</literal></quote>.</para>
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214
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215 <para>MQ works with <emphasis>unified</emphasis> diffs
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216 (<command>patch</command> can accept several other diff formats,
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217 but MQ doesn't). A unified diff contains two kinds of header.
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218 The <emphasis>file header</emphasis> describes the file being
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219 modified; it contains the name of the file to modify. When
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220 <command>patch</command> sees a new file header, it looks for a
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221 file with that name to start modifying.</para>
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222
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223 <para>After the file header comes a series of
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224 <emphasis>hunks</emphasis>. Each hunk starts with a header;
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225 this identifies the range of line numbers within the file that
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226 the hunk should modify. Following the header, a hunk starts and
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227 ends with a few (usually three) lines of text from the
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228 unmodified file; these are called the
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229 <emphasis>context</emphasis> for the hunk. If there's only a
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230 small amount of context between successive hunks,
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231 <command>diff</command> doesn't print a new hunk header; it just
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232 runs the hunks together, with a few lines of context between
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233 modifications.</para>
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234
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235 <para>Each line of context begins with a space character. Within
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236 the hunk, a line that begins with
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237 <quote><literal>-</literal></quote> means <quote>remove this
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238 line,</quote> while a line that begins with
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239 <quote><literal>+</literal></quote> means <quote>insert this
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240 line.</quote> For example, a line that is modified is
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241 represented by one deletion and one insertion.</para>
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242
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243 <para>We will return to some of the more subtle aspects of patches
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244 later (in section <xref linkend="sec.mq.adv-patch"/>), but you
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245 should have
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246 enough information now to use MQ.</para>
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247
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248 </sect1>
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249 <sect1 id="sec.mq.start">
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250 <title>Getting started with Mercurial Queues</title>
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251
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252 <para>Because MQ is implemented as an extension, you must
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253 explicitly enable before you can use it. (You don't need to
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254 download anything; MQ ships with the standard Mercurial
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255 distribution.) To enable MQ, edit your <filename
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256 role="home">~/.hgrc</filename> file, and add the lines
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257 below.</para>
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258
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259 <programlisting>[extensions]
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260 hgext.mq =</programlisting>
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261
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262 <para>Once the extension is enabled, it will make a number of new
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263 commands available. To verify that the extension is working,
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264 you can use <command role="hg-cmd">hg help</command> to see if
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265 the <command role="hg-ext-mq">qinit</command> command is now
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266 available.</para>
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267
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268 &interaction.mq.qinit-help.help;
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269
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270 <para>You can use MQ with <emphasis>any</emphasis> Mercurial
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271 repository, and its commands only operate within that
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272 repository. To get started, simply prepare the repository using
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273 the <command role="hg-ext-mq">qinit</command> command.</para>
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274
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275 &interaction.mq.tutorial.qinit;
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276
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277 <para>This command creates an empty directory called <filename
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278 role="special" class="directory">.hg/patches</filename>, where
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279 MQ will keep its metadata. As with many Mercurial commands, the
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280 <command role="hg-ext-mq">qinit</command> command prints nothing
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281 if it succeeds.</para>
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282
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283 <sect2>
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284 <title>Creating a new patch</title>
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285
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286 <para>To begin work on a new patch, use the <command
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287 role="hg-ext-mq">qnew</command> command. This command takes
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288 one argument, the name of the patch to create.</para>
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289
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290 <para>MQ will use this as the name of an actual file in the
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291 <filename role="special"
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292 class="directory">.hg/patches</filename> directory, as you
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293 can see below.</para>
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294
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295 &interaction.mq.tutorial.qnew;
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296
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297 <para>Also newly present in the <filename role="special"
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298 class="directory">.hg/patches</filename> directory are two
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299 other files, <filename role="special">series</filename> and
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300 <filename role="special">status</filename>. The <filename
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301 role="special">series</filename> file lists all of the
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302 patches that MQ knows about for this repository, with one
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303 patch per line. Mercurial uses the <filename
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304 role="special">status</filename> file for internal
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305 book-keeping; it tracks all of the patches that MQ has
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306 <emphasis>applied</emphasis> in this repository.</para>
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307
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308 <note>
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309 <para> You may sometimes want to edit the <filename
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310 role="special">series</filename> file by hand; for
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311 example, to change the sequence in which some patches are
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312 applied. However, manually editing the <filename
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313 role="special">status</filename> file is almost always a
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314 bad idea, as it's easy to corrupt MQ's idea of what is
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315 happening.</para>
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316 </note>
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317
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318 <para>Once you have created your new patch, you can edit files
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319 in the working directory as you usually would. All of the
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320 normal Mercurial commands, such as <command role="hg-cmd">hg
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321 diff</command> and <command role="hg-cmd">hg
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322 annotate</command>, work exactly as they did before.</para>
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323
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324 </sect2>
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325 <sect2>
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326 <title>Refreshing a patch</title>
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327
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328 <para>When you reach a point where you want to save your work,
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329 use the <command role="hg-ext-mq">qrefresh</command> command
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330 to update the patch you are working on.</para>
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331
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332 &interaction.mq.tutorial.qrefresh;
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333
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334 <para>This command folds the changes you have made in the
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335 working directory into your patch, and updates its
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336 corresponding changeset to contain those changes.</para>
|
bos@559
|
337
|
bos@559
|
338 <para>You can run <command role="hg-ext-mq">qrefresh</command>
|
bos@559
|
339 as often as you like, so it's a good way to
|
bos@559
|
340 <quote>checkpoint</quote> your work. Refresh your patch at an
|
bos@559
|
341 opportune time; try an experiment; and if the experiment
|
bos@558
|
342 doesn't work out, <command role="hg-cmd">hg revert</command>
|
bos@558
|
343 your modifications back to the last time you refreshed.</para>
|
bos@558
|
344
|
bos@567
|
345 &interaction.mq.tutorial.qrefresh2;
|
bos@558
|
346
|
bos@558
|
347 </sect2>
|
bos@558
|
348 <sect2>
|
bos@558
|
349 <title>Stacking and tracking patches</title>
|
bos@558
|
350
|
bos@558
|
351 <para>Once you have finished working on a patch, or need to work
|
bos@559
|
352 on another, you can use the <command
|
bos@559
|
353 role="hg-ext-mq">qnew</command> command again to create a
|
bos@559
|
354 new patch. Mercurial will apply this patch on top of your
|
bos@559
|
355 existing patch.</para>
|
bos@559
|
356
|
bos@567
|
357 &interaction.mq.tutorial.qnew2;
|
bos@559
|
358 <para>Notice that the patch contains the changes in our prior
|
bos@559
|
359 patch as part of its context (you can see this more clearly in
|
bos@559
|
360 the output of <command role="hg-cmd">hg
|
bos@558
|
361 annotate</command>).</para>
|
bos@558
|
362
|
bos@558
|
363 <para>So far, with the exception of <command
|
bos@559
|
364 role="hg-ext-mq">qnew</command> and <command
|
bos@559
|
365 role="hg-ext-mq">qrefresh</command>, we've been careful to
|
bos@558
|
366 only use regular Mercurial commands. However, MQ provides
|
bos@558
|
367 many commands that are easier to use when you are thinking
|
bos@559
|
368 about patches, as illustrated below.</para>
|
bos@559
|
369
|
bos@567
|
370 &interaction.mq.tutorial.qseries;
|
bos@558
|
371
|
bos@558
|
372 <itemizedlist>
|
bos@558
|
373 <listitem><para>The <command
|
bos@559
|
374 role="hg-ext-mq">qseries</command> command lists every
|
bos@558
|
375 patch that MQ knows about in this repository, from oldest
|
bos@558
|
376 to newest (most recently
|
bos@559
|
377 <emphasis>created</emphasis>).</para>
|
bos@559
|
378 </listitem>
|
bos@558
|
379 <listitem><para>The <command
|
bos@559
|
380 role="hg-ext-mq">qapplied</command> command lists every
|
bos@558
|
381 patch that MQ has <emphasis>applied</emphasis> in this
|
bos@558
|
382 repository, again from oldest to newest (most recently
|
bos@559
|
383 applied).</para>
|
bos@559
|
384 </listitem></itemizedlist>
|
bos@558
|
385
|
bos@558
|
386 </sect2>
|
bos@558
|
387 <sect2>
|
bos@558
|
388 <title>Manipulating the patch stack</title>
|
bos@558
|
389
|
bos@558
|
390 <para>The previous discussion implied that there must be a
|
bos@558
|
391 difference between <quote>known</quote> and
|
bos@558
|
392 <quote>applied</quote> patches, and there is. MQ can manage a
|
bos@558
|
393 patch without it being applied in the repository.</para>
|
bos@558
|
394
|
bos@558
|
395 <para>An <emphasis>applied</emphasis> patch has a corresponding
|
bos@558
|
396 changeset in the repository, and the effects of the patch and
|
bos@558
|
397 changeset are visible in the working directory. You can undo
|
bos@558
|
398 the application of a patch using the <command
|
bos@559
|
399 role="hg-ext-mq">qpop</command> command. MQ still
|
bos@558
|
400 <emphasis>knows about</emphasis>, or manages, a popped patch,
|
bos@558
|
401 but the patch no longer has a corresponding changeset in the
|
bos@558
|
402 repository, and the working directory does not contain the
|
bos@558
|
403 changes made by the patch. Figure <xref
|
dongsheng@640
|
404 endterm="fig.mq.stack.caption" linkend="fig.mq.stack"/> illustrates
|
bos@559
|
405 the difference between applied and tracked patches.</para>
|
bos@558
|
406
|
dongsheng@625
|
407 <informalfigure id="fig.mq.stack">
|
dongsheng@640
|
408 <mediaobject>
|
dongsheng@640
|
409 <imageobject><imagedata fileref="images/mq-stack.png"/></imageobject>
|
dongsheng@640
|
410 <textobject><phrase>XXX add text</phrase></textobject>
|
dongsheng@640
|
411 <caption><para id="fig.mq.stack.caption">Applied and unapplied patches
|
dongsheng@640
|
412 in the MQ patch stack</para></caption>
|
dongsheng@640
|
413 </mediaobject>
|
bos@558
|
414 </informalfigure>
|
bos@558
|
415
|
bos@558
|
416 <para>You can reapply an unapplied, or popped, patch using the
|
bos@559
|
417 <command role="hg-ext-mq">qpush</command> command. This
|
bos@558
|
418 creates a new changeset to correspond to the patch, and the
|
bos@558
|
419 patch's changes once again become present in the working
|
bos@559
|
420 directory. See below for examples of <command
|
bos@559
|
421 role="hg-ext-mq">qpop</command> and <command
|
bos@559
|
422 role="hg-ext-mq">qpush</command> in action.</para>
|
bos@567
|
423 &interaction.mq.tutorial.qpop;
|
bos@558
|
424
|
bos@559
|
425 <para>Notice that once we have popped a patch or two patches,
|
bos@559
|
426 the output of <command role="hg-ext-mq">qseries</command>
|
bos@559
|
427 remains the same, while that of <command
|
bos@559
|
428 role="hg-ext-mq">qapplied</command> has changed.</para>
|
bos@559
|
429
|
bos@559
|
430
|
bos@558
|
431 </sect2>
|
bos@558
|
432 <sect2>
|
bos@558
|
433 <title>Pushing and popping many patches</title>
|
bos@558
|
434
|
bos@559
|
435 <para>While <command role="hg-ext-mq">qpush</command> and
|
bos@559
|
436 <command role="hg-ext-mq">qpop</command> each operate on a
|
bos@558
|
437 single patch at a time by default, you can push and pop many
|
bos@558
|
438 patches in one go. The <option
|
bos@559
|
439 role="hg-ext-mq-cmd-qpush-opt">hg -a</option> option to
|
bos@559
|
440 <command role="hg-ext-mq">qpush</command> causes it to push
|
bos@558
|
441 all unapplied patches, while the <option
|
bos@558
|
442 role="hg-ext-mq-cmd-qpop-opt">-a</option> option to <command
|
bos@559
|
443 role="hg-ext-mq">qpop</command> causes it to pop all applied
|
bos@558
|
444 patches. (For some more ways to push and pop many patches,
|
dongsheng@625
|
445 see section <xref linkend="sec.mq.perf"/>
|
bos@559
|
446 below.)</para>
|
bos@558
|
447
|
bos@567
|
448 &interaction.mq.tutorial.qpush-a;
|
bos@558
|
449
|
bos@558
|
450 </sect2>
|
bos@558
|
451 <sect2>
|
bos@558
|
452 <title>Safety checks, and overriding them</title>
|
bos@558
|
453
|
bos@558
|
454 <para>Several MQ commands check the working directory before
|
bos@558
|
455 they do anything, and fail if they find any modifications.
|
bos@558
|
456 They do this to ensure that you won't lose any changes that
|
bos@559
|
457 you have made, but not yet incorporated into a patch. The
|
bos@559
|
458 example below illustrates this; the <command
|
bos@559
|
459 role="hg-ext-mq">qnew</command> command will not create a
|
bos@558
|
460 new patch if there are outstanding changes, caused in this
|
bos@558
|
461 case by the <command role="hg-cmd">hg add</command> of
|
bos@558
|
462 <filename>file3</filename>.</para>
|
bos@558
|
463
|
bos@567
|
464 &interaction.mq.tutorial.add;
|
bos@558
|
465
|
bos@558
|
466 <para>Commands that check the working directory all take an
|
bos@558
|
467 <quote>I know what I'm doing</quote> option, which is always
|
bos@558
|
468 named <option>-f</option>. The exact meaning of
|
bos@558
|
469 <option>-f</option> depends on the command. For example,
|
bos@558
|
470 <command role="hg-cmd">hg qnew <option
|
bos@559
|
471 role="hg-ext-mq-cmd-qnew-opt">hg -f</option></command>
|
bos@559
|
472 will incorporate any outstanding changes into the new patch it
|
bos@558
|
473 creates, but <command role="hg-cmd">hg qpop <option
|
bos@559
|
474 role="hg-ext-mq-cmd-qpop-opt">hg -f</option></command>
|
bos@559
|
475 will revert modifications to any files affected by the patch
|
bos@559
|
476 that it is popping. Be sure to read the documentation for a
|
bos@558
|
477 command's <option>-f</option> option before you use it!</para>
|
bos@558
|
478
|
bos@558
|
479 </sect2>
|
bos@558
|
480 <sect2>
|
bos@558
|
481 <title>Working on several patches at once</title>
|
bos@558
|
482
|
bos@559
|
483 <para>The <command role="hg-ext-mq">qrefresh</command> command
|
bos@558
|
484 always refreshes the <emphasis>topmost</emphasis> applied
|
bos@558
|
485 patch. This means that you can suspend work on one patch (by
|
bos@558
|
486 refreshing it), pop or push to make a different patch the top,
|
bos@558
|
487 and work on <emphasis>that</emphasis> patch for a
|
bos@558
|
488 while.</para>
|
bos@558
|
489
|
bos@558
|
490 <para>Here's an example that illustrates how you can use this
|
bos@558
|
491 ability. Let's say you're developing a new feature as two
|
bos@558
|
492 patches. The first is a change to the core of your software,
|
bos@559
|
493 and the second&emdash;layered on top of the
|
bos@559
|
494 first&emdash;changes the user interface to use the code you
|
bos@559
|
495 just added to the core. If you notice a bug in the core while
|
bos@559
|
496 you're working on the UI patch, it's easy to fix the core.
|
bos@559
|
497 Simply <command role="hg-ext-mq">qrefresh</command> the UI
|
bos@559
|
498 patch to save your in-progress changes, and <command
|
bos@559
|
499 role="hg-ext-mq">qpop</command> down to the core patch. Fix
|
bos@559
|
500 the core bug, <command role="hg-ext-mq">qrefresh</command> the
|
bos@559
|
501 core patch, and <command role="hg-ext-mq">qpush</command> back
|
bos@558
|
502 to the UI patch to continue where you left off.</para>
|
bos@558
|
503
|
bos@558
|
504 </sect2>
|
bos@558
|
505 </sect1>
|
dongsheng@625
|
506 <sect1 id="sec.mq.adv-patch">
|
bos@558
|
507 <title>More about patches</title>
|
bos@558
|
508
|
bos@558
|
509 <para>MQ uses the GNU <command>patch</command> command to apply
|
bos@558
|
510 patches, so it's helpful to know a few more detailed aspects of
|
bos@558
|
511 how <command>patch</command> works, and about patches
|
bos@558
|
512 themselves.</para>
|
bos@558
|
513
|
bos@558
|
514 <sect2>
|
bos@558
|
515 <title>The strip count</title>
|
bos@558
|
516
|
bos@558
|
517 <para>If you look at the file headers in a patch, you will
|
bos@558
|
518 notice that the pathnames usually have an extra component on
|
bos@558
|
519 the front that isn't present in the actual path name. This is
|
bos@558
|
520 a holdover from the way that people used to generate patches
|
bos@558
|
521 (people still do this, but it's somewhat rare with modern
|
bos@558
|
522 revision control tools).</para>
|
bos@558
|
523
|
bos@558
|
524 <para>Alice would unpack a tarball, edit her files, then decide
|
bos@558
|
525 that she wanted to create a patch. So she'd rename her
|
bos@558
|
526 working directory, unpack the tarball again (hence the need
|
bos@558
|
527 for the rename), and use the <option
|
bos@558
|
528 role="cmd-opt-diff">-r</option> and <option
|
bos@558
|
529 role="cmd-opt-diff">-N</option> options to
|
bos@558
|
530 <command>diff</command> to recursively generate a patch
|
bos@558
|
531 between the unmodified directory and the modified one. The
|
bos@558
|
532 result would be that the name of the unmodified directory
|
bos@558
|
533 would be at the front of the left-hand path in every file
|
bos@558
|
534 header, and the name of the modified directory would be at the
|
bos@558
|
535 front of the right-hand path.</para>
|
bos@558
|
536
|
bos@558
|
537 <para>Since someone receiving a patch from the Alices of the net
|
bos@558
|
538 would be unlikely to have unmodified and modified directories
|
bos@558
|
539 with exactly the same names, the <command>patch</command>
|
bos@558
|
540 command has a <option role="cmd-opt-patch">-p</option> option
|
bos@558
|
541 that indicates the number of leading path name components to
|
bos@558
|
542 strip when trying to apply a patch. This number is called the
|
bos@558
|
543 <emphasis>strip count</emphasis>.</para>
|
bos@558
|
544
|
bos@558
|
545 <para>An option of <quote><literal>-p1</literal></quote> means
|
bos@558
|
546 <quote>use a strip count of one</quote>. If
|
bos@558
|
547 <command>patch</command> sees a file name
|
bos@558
|
548 <filename>foo/bar/baz</filename> in a file header, it will
|
bos@558
|
549 strip <filename>foo</filename> and try to patch a file named
|
bos@558
|
550 <filename>bar/baz</filename>. (Strictly speaking, the strip
|
bos@558
|
551 count refers to the number of <emphasis>path
|
bos@558
|
552 separators</emphasis> (and the components that go with them
|
bos@558
|
553 ) to strip. A strip count of one will turn
|
bos@558
|
554 <filename>foo/bar</filename> into <filename>bar</filename>,
|
bos@558
|
555 but <filename>/foo/bar</filename> (notice the extra leading
|
bos@558
|
556 slash) into <filename>foo/bar</filename>.)</para>
|
bos@558
|
557
|
bos@558
|
558 <para>The <quote>standard</quote> strip count for patches is
|
bos@558
|
559 one; almost all patches contain one leading path name
|
bos@558
|
560 component that needs to be stripped. Mercurial's <command
|
bos@558
|
561 role="hg-cmd">hg diff</command> command generates path names
|
bos@558
|
562 in this form, and the <command role="hg-cmd">hg
|
bos@558
|
563 import</command> command and MQ expect patches to have a
|
bos@558
|
564 strip count of one.</para>
|
bos@558
|
565
|
bos@558
|
566 <para>If you receive a patch from someone that you want to add
|
bos@558
|
567 to your patch queue, and the patch needs a strip count other
|
bos@558
|
568 than one, you cannot just <command
|
bos@559
|
569 role="hg-ext-mq">qimport</command> the patch, because
|
bos@559
|
570 <command role="hg-ext-mq">qimport</command> does not yet have
|
bos@558
|
571 a <literal>-p</literal> option (see <ulink role="hg-bug"
|
bos@558
|
572 url="http://www.selenic.com/mercurial/bts/issue311">issue
|
bos@558
|
573 311</ulink>). Your best bet is to <command
|
bos@559
|
574 role="hg-ext-mq">qnew</command> a patch of your own, then
|
bos@558
|
575 use <command>patch -pN</command> to apply their patch,
|
bos@558
|
576 followed by <command role="hg-cmd">hg addremove</command> to
|
bos@558
|
577 pick up any files added or removed by the patch, followed by
|
bos@559
|
578 <command role="hg-ext-mq">hg qrefresh</command>. This
|
bos@559
|
579 complexity may become unnecessary; see <ulink role="hg-bug"
|
bos@558
|
580 url="http://www.selenic.com/mercurial/bts/issue311">issue
|
bos@559
|
581 311</ulink> for details.
|
bos@559
|
582 </para>
|
bos@558
|
583 </sect2>
|
bos@558
|
584 <sect2>
|
bos@558
|
585 <title>Strategies for applying a patch</title>
|
bos@558
|
586
|
bos@558
|
587 <para>When <command>patch</command> applies a hunk, it tries a
|
bos@558
|
588 handful of successively less accurate strategies to try to
|
bos@558
|
589 make the hunk apply. This falling-back technique often makes
|
bos@558
|
590 it possible to take a patch that was generated against an old
|
bos@558
|
591 version of a file, and apply it against a newer version of
|
bos@558
|
592 that file.</para>
|
bos@558
|
593
|
bos@558
|
594 <para>First, <command>patch</command> tries an exact match,
|
bos@558
|
595 where the line numbers, the context, and the text to be
|
bos@558
|
596 modified must apply exactly. If it cannot make an exact
|
bos@558
|
597 match, it tries to find an exact match for the context,
|
bos@558
|
598 without honouring the line numbering information. If this
|
bos@558
|
599 succeeds, it prints a line of output saying that the hunk was
|
bos@558
|
600 applied, but at some <emphasis>offset</emphasis> from the
|
bos@558
|
601 original line number.</para>
|
bos@558
|
602
|
bos@558
|
603 <para>If a context-only match fails, <command>patch</command>
|
bos@558
|
604 removes the first and last lines of the context, and tries a
|
bos@558
|
605 <emphasis>reduced</emphasis> context-only match. If the hunk
|
bos@558
|
606 with reduced context succeeds, it prints a message saying that
|
bos@558
|
607 it applied the hunk with a <emphasis>fuzz factor</emphasis>
|
bos@558
|
608 (the number after the fuzz factor indicates how many lines of
|
bos@558
|
609 context <command>patch</command> had to trim before the patch
|
bos@558
|
610 applied).</para>
|
bos@558
|
611
|
bos@558
|
612 <para>When neither of these techniques works,
|
bos@558
|
613 <command>patch</command> prints a message saying that the hunk
|
bos@558
|
614 in question was rejected. It saves rejected hunks (also
|
bos@558
|
615 simply called <quote>rejects</quote>) to a file with the same
|
bos@558
|
616 name, and an added <filename role="special">.rej</filename>
|
bos@558
|
617 extension. It also saves an unmodified copy of the file with
|
bos@558
|
618 a <filename role="special">.orig</filename> extension; the
|
bos@558
|
619 copy of the file without any extensions will contain any
|
bos@558
|
620 changes made by hunks that <emphasis>did</emphasis> apply
|
bos@558
|
621 cleanly. If you have a patch that modifies
|
bos@558
|
622 <filename>foo</filename> with six hunks, and one of them fails
|
bos@558
|
623 to apply, you will have: an unmodified
|
bos@558
|
624 <filename>foo.orig</filename>, a <filename>foo.rej</filename>
|
bos@558
|
625 containing one hunk, and <filename>foo</filename>, containing
|
bos@558
|
626 the changes made by the five successful hunks.</para>
|
bos@558
|
627
|
bos@558
|
628 </sect2>
|
bos@558
|
629 <sect2>
|
bos@558
|
630 <title>Some quirks of patch representation</title>
|
bos@558
|
631
|
bos@558
|
632 <para>There are a few useful things to know about how
|
bos@558
|
633 <command>patch</command> works with files.</para>
|
bos@558
|
634 <itemizedlist>
|
bos@558
|
635 <listitem><para>This should already be obvious, but
|
bos@558
|
636 <command>patch</command> cannot handle binary
|
bos@559
|
637 files.</para>
|
bos@559
|
638 </listitem>
|
bos@558
|
639 <listitem><para>Neither does it care about the executable bit;
|
bos@558
|
640 it creates new files as readable, but not
|
bos@559
|
641 executable.</para>
|
bos@559
|
642 </listitem>
|
bos@558
|
643 <listitem><para><command>patch</command> treats the removal of
|
bos@558
|
644 a file as a diff between the file to be removed and the
|
bos@558
|
645 empty file. So your idea of <quote>I deleted this
|
bos@558
|
646 file</quote> looks like <quote>every line of this file
|
bos@559
|
647 was deleted</quote> in a patch.</para>
|
bos@559
|
648 </listitem>
|
bos@558
|
649 <listitem><para>It treats the addition of a file as a diff
|
bos@558
|
650 between the empty file and the file to be added. So in a
|
bos@558
|
651 patch, your idea of <quote>I added this file</quote> looks
|
bos@558
|
652 like <quote>every line of this file was
|
bos@559
|
653 added</quote>.</para>
|
bos@559
|
654 </listitem>
|
bos@558
|
655 <listitem><para>It treats a renamed file as the removal of the
|
bos@558
|
656 old name, and the addition of the new name. This means
|
bos@558
|
657 that renamed files have a big footprint in patches. (Note
|
bos@558
|
658 also that Mercurial does not currently try to infer when
|
bos@559
|
659 files have been renamed or copied in a patch.)</para>
|
bos@559
|
660 </listitem>
|
bos@558
|
661 <listitem><para><command>patch</command> cannot represent
|
bos@558
|
662 empty files, so you cannot use a patch to represent the
|
bos@558
|
663 notion <quote>I added this empty file to the
|
bos@559
|
664 tree</quote>.</para>
|
bos@559
|
665 </listitem></itemizedlist>
|
bos@559
|
666 </sect2>
|
bos@558
|
667 <sect2>
|
bos@558
|
668 <title>Beware the fuzz</title>
|
bos@558
|
669
|
bos@558
|
670 <para>While applying a hunk at an offset, or with a fuzz factor,
|
bos@558
|
671 will often be completely successful, these inexact techniques
|
bos@558
|
672 naturally leave open the possibility of corrupting the patched
|
bos@558
|
673 file. The most common cases typically involve applying a
|
bos@558
|
674 patch twice, or at an incorrect location in the file. If
|
bos@558
|
675 <command>patch</command> or <command
|
bos@559
|
676 role="hg-ext-mq">qpush</command> ever mentions an offset or
|
bos@558
|
677 fuzz factor, you should make sure that the modified files are
|
bos@558
|
678 correct afterwards.</para>
|
bos@558
|
679
|
bos@558
|
680 <para>It's often a good idea to refresh a patch that has applied
|
bos@558
|
681 with an offset or fuzz factor; refreshing the patch generates
|
bos@558
|
682 new context information that will make it apply cleanly. I
|
bos@558
|
683 say <quote>often,</quote> not <quote>always,</quote> because
|
bos@558
|
684 sometimes refreshing a patch will make it fail to apply
|
bos@558
|
685 against a different revision of the underlying files. In some
|
bos@558
|
686 cases, such as when you're maintaining a patch that must sit
|
bos@558
|
687 on top of multiple versions of a source tree, it's acceptable
|
bos@558
|
688 to have a patch apply with some fuzz, provided you've verified
|
bos@558
|
689 the results of the patching process in such cases.</para>
|
bos@558
|
690
|
bos@558
|
691 </sect2>
|
bos@558
|
692 <sect2>
|
bos@558
|
693 <title>Handling rejection</title>
|
bos@558
|
694
|
bos@559
|
695 <para>If <command role="hg-ext-mq">qpush</command> fails to
|
bos@558
|
696 apply a patch, it will print an error message and exit. If it
|
bos@558
|
697 has left <filename role="special">.rej</filename> files
|
bos@558
|
698 behind, it is usually best to fix up the rejected hunks before
|
bos@558
|
699 you push more patches or do any further work.</para>
|
bos@558
|
700
|
bos@558
|
701 <para>If your patch <emphasis>used to</emphasis> apply cleanly,
|
bos@558
|
702 and no longer does because you've changed the underlying code
|
bos@558
|
703 that your patches are based on, Mercurial Queues can help; see
|
bos@559
|
704 section <xref
|
dongsheng@625
|
705 linkend="sec.mq.merge"/> for details.</para>
|
bos@558
|
706
|
bos@558
|
707 <para>Unfortunately, there aren't any great techniques for
|
bos@558
|
708 dealing with rejected hunks. Most often, you'll need to view
|
bos@558
|
709 the <filename role="special">.rej</filename> file and edit the
|
bos@558
|
710 target file, applying the rejected hunks by hand.</para>
|
bos@558
|
711
|
bos@558
|
712 <para>If you're feeling adventurous, Neil Brown, a Linux kernel
|
bos@558
|
713 hacker, wrote a tool called <command>wiggle</command>
|
bos@558
|
714 <citation>web:wiggle</citation>, which is more vigorous than
|
bos@558
|
715 <command>patch</command> in its attempts to make a patch
|
bos@558
|
716 apply.</para>
|
bos@558
|
717
|
bos@558
|
718 <para>Another Linux kernel hacker, Chris Mason (the author of
|
bos@558
|
719 Mercurial Queues), wrote a similar tool called
|
bos@558
|
720 <command>mpatch</command> <citation>web:mpatch</citation>,
|
bos@558
|
721 which takes a simple approach to automating the application of
|
bos@558
|
722 hunks rejected by <command>patch</command>. The
|
bos@558
|
723 <command>mpatch</command> command can help with four common
|
bos@558
|
724 reasons that a hunk may be rejected:</para>
|
bos@558
|
725
|
bos@558
|
726 <itemizedlist>
|
bos@558
|
727 <listitem><para>The context in the middle of a hunk has
|
bos@559
|
728 changed.</para>
|
bos@559
|
729 </listitem>
|
bos@558
|
730 <listitem><para>A hunk is missing some context at the
|
bos@559
|
731 beginning or end.</para>
|
bos@559
|
732 </listitem>
|
bos@558
|
733 <listitem><para>A large hunk might apply better&emdash;either
|
bos@559
|
734 entirely or in part&emdash;if it was broken up into
|
bos@559
|
735 smaller hunks.</para>
|
bos@559
|
736 </listitem>
|
bos@558
|
737 <listitem><para>A hunk removes lines with slightly different
|
bos@559
|
738 content than those currently present in the file.</para>
|
bos@559
|
739 </listitem></itemizedlist>
|
bos@558
|
740
|
bos@558
|
741 <para>If you use <command>wiggle</command> or
|
bos@558
|
742 <command>mpatch</command>, you should be doubly careful to
|
bos@558
|
743 check your results when you're done. In fact,
|
bos@558
|
744 <command>mpatch</command> enforces this method of
|
bos@558
|
745 double-checking the tool's output, by automatically dropping
|
bos@558
|
746 you into a merge program when it has done its job, so that you
|
bos@558
|
747 can verify its work and finish off any remaining
|
bos@558
|
748 merges.</para>
|
bos@558
|
749
|
bos@558
|
750 </sect2>
|
bos@558
|
751 </sect1>
|
dongsheng@625
|
752 <sect1 id="sec.mq.perf">
|
bos@558
|
753 <title>Getting the best performance out of MQ</title>
|
bos@558
|
754
|
bos@558
|
755 <para>MQ is very efficient at handling a large number of patches.
|
bos@558
|
756 I ran some performance experiments in mid-2006 for a talk that I
|
bos@558
|
757 gave at the 2006 EuroPython conference
|
bos@558
|
758 <citation>web:europython</citation>. I used as my data set the
|
bos@558
|
759 Linux 2.6.17-mm1 patch series, which consists of 1,738 patches.
|
bos@558
|
760 I applied these on top of a Linux kernel repository containing
|
bos@558
|
761 all 27,472 revisions between Linux 2.6.12-rc2 and Linux
|
bos@558
|
762 2.6.17.</para>
|
bos@558
|
763
|
bos@558
|
764 <para>On my old, slow laptop, I was able to <command
|
bos@558
|
765 role="hg-cmd">hg qpush <option
|
bos@559
|
766 role="hg-ext-mq-cmd-qpush-opt">hg -a</option></command> all
|
bos@558
|
767 1,738 patches in 3.5 minutes, and <command role="hg-cmd">hg qpop
|
bos@559
|
768 <option role="hg-ext-mq-cmd-qpop-opt">hg -a</option></command>
|
bos@558
|
769 them all in 30 seconds. (On a newer laptop, the time to push
|
bos@558
|
770 all patches dropped to two minutes.) I could <command
|
bos@559
|
771 role="hg-ext-mq">qrefresh</command> one of the biggest patches
|
bos@558
|
772 (which made 22,779 lines of changes to 287 files) in 6.6
|
bos@558
|
773 seconds.</para>
|
bos@558
|
774
|
bos@558
|
775 <para>Clearly, MQ is well suited to working in large trees, but
|
bos@558
|
776 there are a few tricks you can use to get the best performance
|
bos@558
|
777 of it.</para>
|
bos@558
|
778
|
bos@558
|
779 <para>First of all, try to <quote>batch</quote> operations
|
bos@558
|
780 together. Every time you run <command
|
bos@559
|
781 role="hg-ext-mq">qpush</command> or <command
|
bos@559
|
782 role="hg-ext-mq">qpop</command>, these commands scan the
|
bos@558
|
783 working directory once to make sure you haven't made some
|
bos@558
|
784 changes and then forgotten to run <command
|
bos@559
|
785 role="hg-ext-mq">qrefresh</command>. On a small tree, the
|
bos@558
|
786 time that this scan takes is unnoticeable. However, on a
|
bos@558
|
787 medium-sized tree (containing tens of thousands of files), it
|
bos@558
|
788 can take a second or more.</para>
|
bos@558
|
789
|
bos@559
|
790 <para>The <command role="hg-ext-mq">qpush</command> and <command
|
bos@559
|
791 role="hg-ext-mq">qpop</command> commands allow you to push and
|
bos@558
|
792 pop multiple patches at a time. You can identify the
|
bos@558
|
793 <quote>destination patch</quote> that you want to end up at.
|
bos@559
|
794 When you <command role="hg-ext-mq">qpush</command> with a
|
bos@558
|
795 destination specified, it will push patches until that patch is
|
bos@558
|
796 at the top of the applied stack. When you <command
|
bos@559
|
797 role="hg-ext-mq">qpop</command> to a destination, MQ will pop
|
bos@558
|
798 patches until the destination patch is at the top.</para>
|
bos@558
|
799
|
bos@558
|
800 <para>You can identify a destination patch using either the name
|
bos@558
|
801 of the patch, or by number. If you use numeric addressing,
|
bos@558
|
802 patches are counted from zero; this means that the first patch
|
bos@558
|
803 is zero, the second is one, and so on.</para>
|
bos@558
|
804
|
bos@558
|
805 </sect1>
|
dongsheng@625
|
806 <sect1 id="sec.mq.merge">
|
bos@558
|
807 <title>Updating your patches when the underlying code
|
bos@558
|
808 changes</title>
|
bos@558
|
809
|
bos@558
|
810 <para>It's common to have a stack of patches on top of an
|
bos@558
|
811 underlying repository that you don't modify directly. If you're
|
bos@558
|
812 working on changes to third-party code, or on a feature that is
|
bos@558
|
813 taking longer to develop than the rate of change of the code
|
bos@558
|
814 beneath, you will often need to sync up with the underlying
|
bos@558
|
815 code, and fix up any hunks in your patches that no longer apply.
|
bos@558
|
816 This is called <emphasis>rebasing</emphasis> your patch
|
bos@558
|
817 series.</para>
|
bos@558
|
818
|
bos@558
|
819 <para>The simplest way to do this is to <command role="hg-cmd">hg
|
bos@559
|
820 qpop <option role="hg-ext-mq-cmd-qpop-opt">hg
|
bos@559
|
821 -a</option></command> your patches, then <command
|
bos@559
|
822 role="hg-cmd">hg pull</command> changes into the underlying
|
bos@559
|
823 repository, and finally <command role="hg-cmd">hg qpush <option
|
bos@559
|
824 role="hg-ext-mq-cmd-qpop-opt">hg -a</option></command> your
|
bos@558
|
825 patches again. MQ will stop pushing any time it runs across a
|
bos@558
|
826 patch that fails to apply during conflicts, allowing you to fix
|
bos@559
|
827 your conflicts, <command role="hg-ext-mq">qrefresh</command> the
|
bos@558
|
828 affected patch, and continue pushing until you have fixed your
|
bos@558
|
829 entire stack.</para>
|
bos@558
|
830
|
bos@558
|
831 <para>This approach is easy to use and works well if you don't
|
bos@558
|
832 expect changes to the underlying code to affect how well your
|
bos@558
|
833 patches apply. If your patch stack touches code that is modified
|
bos@558
|
834 frequently or invasively in the underlying repository, however,
|
bos@558
|
835 fixing up rejected hunks by hand quickly becomes
|
bos@558
|
836 tiresome.</para>
|
bos@558
|
837
|
bos@559
|
838 <para>It's possible to partially automate the rebasing process.
|
bos@559
|
839 If your patches apply cleanly against some revision of the
|
bos@558
|
840 underlying repo, MQ can use this information to help you to
|
bos@558
|
841 resolve conflicts between your patches and a different
|
bos@558
|
842 revision.</para>
|
bos@558
|
843
|
bos@558
|
844 <para>The process is a little involved.</para>
|
bos@558
|
845 <orderedlist>
|
bos@558
|
846 <listitem><para>To begin, <command role="hg-cmd">hg qpush
|
bos@558
|
847 -a</command> all of your patches on top of the revision
|
bos@559
|
848 where you know that they apply cleanly.</para>
|
bos@559
|
849 </listitem>
|
bos@558
|
850 <listitem><para>Save a backup copy of your patch directory using
|
bos@558
|
851 <command role="hg-cmd">hg qsave <option
|
bos@559
|
852 role="hg-ext-mq-cmd-qsave-opt">hg -e</option> <option
|
bos@559
|
853 role="hg-ext-mq-cmd-qsave-opt">hg -c</option></command>.
|
bos@558
|
854 This prints the name of the directory that it has saved the
|
bos@558
|
855 patches in. It will save the patches to a directory called
|
bos@558
|
856 <filename role="special"
|
bos@558
|
857 class="directory">.hg/patches.N</filename>, where
|
bos@558
|
858 <literal>N</literal> is a small integer. It also commits a
|
bos@558
|
859 <quote>save changeset</quote> on top of your applied
|
bos@558
|
860 patches; this is for internal book-keeping, and records the
|
bos@558
|
861 states of the <filename role="special">series</filename> and
|
bos@559
|
862 <filename role="special">status</filename> files.</para>
|
bos@559
|
863 </listitem>
|
bos@559
|
864 <listitem><para>Use <command role="hg-cmd">hg pull</command> to
|
bos@559
|
865 bring new changes into the underlying repository. (Don't
|
bos@559
|
866 run <command role="hg-cmd">hg pull -u</command>; see below
|
bos@559
|
867 for why.)</para>
|
bos@559
|
868 </listitem>
|
bos@558
|
869 <listitem><para>Update to the new tip revision, using <command
|
bos@558
|
870 role="hg-cmd">hg update <option
|
bos@558
|
871 role="hg-opt-update">-C</option></command> to override
|
bos@559
|
872 the patches you have pushed.</para>
|
bos@559
|
873 </listitem>
|
bos@580
|
874 <listitem><para>Merge all patches using <command>hg qpush -m
|
bos@580
|
875 -a</command>. The <option
|
bos@580
|
876 role="hg-ext-mq-cmd-qpush-opt">-m</option> option to
|
bos@559
|
877 <command role="hg-ext-mq">qpush</command> tells MQ to
|
bos@558
|
878 perform a three-way merge if the patch fails to
|
bos@559
|
879 apply.</para>
|
bos@559
|
880 </listitem></orderedlist>
|
bos@558
|
881
|
bos@558
|
882 <para>During the <command role="hg-cmd">hg qpush <option
|
bos@559
|
883 role="hg-ext-mq-cmd-qpush-opt">hg -m</option></command>,
|
bos@559
|
884 each patch in the <filename role="special">series</filename>
|
bos@559
|
885 file is applied normally. If a patch applies with fuzz or
|
bos@559
|
886 rejects, MQ looks at the queue you <command
|
bos@559
|
887 role="hg-ext-mq">qsave</command>d, and performs a three-way
|
bos@558
|
888 merge with the corresponding changeset. This merge uses
|
bos@558
|
889 Mercurial's normal merge machinery, so it may pop up a GUI merge
|
bos@558
|
890 tool to help you to resolve problems.</para>
|
bos@558
|
891
|
bos@558
|
892 <para>When you finish resolving the effects of a patch, MQ
|
bos@558
|
893 refreshes your patch based on the result of the merge.</para>
|
bos@558
|
894
|
bos@558
|
895 <para>At the end of this process, your repository will have one
|
bos@558
|
896 extra head from the old patch queue, and a copy of the old patch
|
bos@558
|
897 queue will be in <filename role="special"
|
bos@558
|
898 class="directory">.hg/patches.N</filename>. You can remove the
|
bos@559
|
899 extra head using <command role="hg-cmd">hg qpop -a -n
|
bos@558
|
900 patches.N</command> or <command role="hg-cmd">hg
|
bos@558
|
901 strip</command>. You can delete <filename role="special"
|
bos@558
|
902 class="directory">.hg/patches.N</filename> once you are sure
|
bos@558
|
903 that you no longer need it as a backup.</para>
|
bos@558
|
904
|
bos@558
|
905 </sect1>
|
bos@558
|
906 <sect1>
|
bos@558
|
907 <title>Identifying patches</title>
|
bos@558
|
908
|
bos@558
|
909 <para>MQ commands that work with patches let you refer to a patch
|
bos@558
|
910 either by using its name or by a number. By name is obvious
|
bos@558
|
911 enough; pass the name <filename>foo.patch</filename> to <command
|
bos@559
|
912 role="hg-ext-mq">qpush</command>, for example, and it will
|
bos@558
|
913 push patches until <filename>foo.patch</filename> is
|
bos@558
|
914 applied.</para>
|
bos@558
|
915
|
bos@558
|
916 <para>As a shortcut, you can refer to a patch using both a name
|
bos@558
|
917 and a numeric offset; <literal>foo.patch-2</literal> means
|
bos@558
|
918 <quote>two patches before <literal>foo.patch</literal></quote>,
|
bos@558
|
919 while <literal>bar.patch+4</literal> means <quote>four patches
|
bos@558
|
920 after <literal>bar.patch</literal></quote>.</para>
|
bos@558
|
921
|
bos@558
|
922 <para>Referring to a patch by index isn't much different. The
|
bos@558
|
923 first patch printed in the output of <command
|
bos@559
|
924 role="hg-ext-mq">qseries</command> is patch zero (yes, it's
|
bos@558
|
925 one of those start-at-zero counting systems); the second is
|
bos@558
|
926 patch one; and so on.</para>
|
bos@558
|
927
|
bos@558
|
928 <para>MQ also makes it easy to work with patches when you are
|
bos@558
|
929 using normal Mercurial commands. Every command that accepts a
|
bos@558
|
930 changeset ID will also accept the name of an applied patch. MQ
|
bos@558
|
931 augments the tags normally in the repository with an eponymous
|
bos@558
|
932 one for each applied patch. In addition, the special tags
|
bos@580
|
933 <literal role="tag">qbase</literal> and
|
bos@580
|
934 <literal role="tag">qtip</literal> identify
|
bos@558
|
935 the <quote>bottom-most</quote> and topmost applied patches,
|
bos@558
|
936 respectively.</para>
|
bos@558
|
937
|
bos@558
|
938 <para>These additions to Mercurial's normal tagging capabilities
|
bos@558
|
939 make dealing with patches even more of a breeze.</para>
|
bos@558
|
940 <itemizedlist>
|
bos@558
|
941 <listitem><para>Want to patchbomb a mailing list with your
|
bos@558
|
942 latest series of changes?</para>
|
bos@580
|
943 <programlisting>hg email qbase:qtip</programlisting>
|
bos@559
|
944 <para> (Don't know what <quote>patchbombing</quote> is? See
|
dongsheng@625
|
945 section <xref linkend="sec.hgext.patchbomb"/>.)</para>
|
bos@559
|
946 </listitem>
|
bos@558
|
947 <listitem><para>Need to see all of the patches since
|
bos@558
|
948 <literal>foo.patch</literal> that have touched files in a
|
bos@558
|
949 subdirectory of your tree?</para>
|
bos@580
|
950 <programlisting>hg log -r foo.patch:qtip subdir</programlisting>
|
bos@559
|
951 </listitem>
|
bos@558
|
952 </itemizedlist>
|
bos@558
|
953
|
bos@558
|
954 <para>Because MQ makes the names of patches available to the rest
|
bos@558
|
955 of Mercurial through its normal internal tag machinery, you
|
bos@558
|
956 don't need to type in the entire name of a patch when you want
|
bos@558
|
957 to identify it by name.</para>
|
bos@558
|
958
|
bos@558
|
959 <para>Another nice consequence of representing patch names as tags
|
bos@558
|
960 is that when you run the <command role="hg-cmd">hg log</command>
|
bos@558
|
961 command, it will display a patch's name as a tag, simply as part
|
bos@558
|
962 of its normal output. This makes it easy to visually
|
bos@558
|
963 distinguish applied patches from underlying
|
bos@559
|
964 <quote>normal</quote> revisions. The following example shows a
|
bos@559
|
965 few normal Mercurial commands in use with applied
|
bos@559
|
966 patches.</para>
|
bos@559
|
967
|
bos@567
|
968 &interaction.mq.id.output;
|
bos@558
|
969
|
bos@558
|
970 </sect1>
|
bos@558
|
971 <sect1>
|
bos@558
|
972 <title>Useful things to know about</title>
|
bos@558
|
973
|
bos@558
|
974 <para>There are a number of aspects of MQ usage that don't fit
|
bos@558
|
975 tidily into sections of their own, but that are good to know.
|
bos@558
|
976 Here they are, in one place.</para>
|
bos@558
|
977
|
bos@558
|
978 <itemizedlist>
|
bos@558
|
979 <listitem><para>Normally, when you <command
|
bos@559
|
980 role="hg-ext-mq">qpop</command> a patch and <command
|
bos@559
|
981 role="hg-ext-mq">qpush</command> it again, the changeset
|
bos@558
|
982 that represents the patch after the pop/push will have a
|
bos@558
|
983 <emphasis>different identity</emphasis> than the changeset
|
bos@558
|
984 that represented the hash beforehand. See section <xref
|
dongsheng@625
|
985 linkend="sec.mqref.cmd.qpush"/> for
|
bos@559
|
986 information as to why this is.</para>
|
bos@559
|
987 </listitem>
|
bos@558
|
988 <listitem><para>It's not a good idea to <command
|
bos@558
|
989 role="hg-cmd">hg merge</command> changes from another
|
bos@558
|
990 branch with a patch changeset, at least if you want to
|
bos@558
|
991 maintain the <quote>patchiness</quote> of that changeset and
|
bos@558
|
992 changesets below it on the patch stack. If you try to do
|
bos@558
|
993 this, it will appear to succeed, but MQ will become
|
bos@559
|
994 confused.</para>
|
bos@559
|
995 </listitem></itemizedlist>
|
bos@559
|
996
|
bos@559
|
997 </sect1>
|
dongsheng@625
|
998 <sect1 id="sec.mq.repo">
|
bos@558
|
999 <title>Managing patches in a repository</title>
|
bos@558
|
1000
|
bos@558
|
1001 <para>Because MQ's <filename role="special"
|
bos@558
|
1002 class="directory">.hg/patches</filename> directory resides
|
bos@558
|
1003 outside a Mercurial repository's working directory, the
|
bos@558
|
1004 <quote>underlying</quote> Mercurial repository knows nothing
|
bos@558
|
1005 about the management or presence of patches.</para>
|
bos@558
|
1006
|
bos@558
|
1007 <para>This presents the interesting possibility of managing the
|
bos@558
|
1008 contents of the patch directory as a Mercurial repository in its
|
bos@558
|
1009 own right. This can be a useful way to work. For example, you
|
bos@558
|
1010 can work on a patch for a while, <command
|
bos@559
|
1011 role="hg-ext-mq">qrefresh</command> it, then <command
|
bos@558
|
1012 role="hg-cmd">hg commit</command> the current state of the
|
bos@558
|
1013 patch. This lets you <quote>roll back</quote> to that version
|
bos@558
|
1014 of the patch later on.</para>
|
bos@558
|
1015
|
bos@558
|
1016 <para>You can then share different versions of the same patch
|
bos@558
|
1017 stack among multiple underlying repositories. I use this when I
|
bos@558
|
1018 am developing a Linux kernel feature. I have a pristine copy of
|
bos@558
|
1019 my kernel sources for each of several CPU architectures, and a
|
bos@558
|
1020 cloned repository under each that contains the patches I am
|
bos@558
|
1021 working on. When I want to test a change on a different
|
bos@558
|
1022 architecture, I push my current patches to the patch repository
|
bos@558
|
1023 associated with that kernel tree, pop and push all of my
|
bos@558
|
1024 patches, and build and test that kernel.</para>
|
bos@558
|
1025
|
bos@558
|
1026 <para>Managing patches in a repository makes it possible for
|
bos@558
|
1027 multiple developers to work on the same patch series without
|
bos@558
|
1028 colliding with each other, all on top of an underlying source
|
bos@558
|
1029 base that they may or may not control.</para>
|
bos@558
|
1030
|
bos@558
|
1031 <sect2>
|
bos@558
|
1032 <title>MQ support for patch repositories</title>
|
bos@558
|
1033
|
bos@558
|
1034 <para>MQ helps you to work with the <filename role="special"
|
bos@558
|
1035 class="directory">.hg/patches</filename> directory as a
|
bos@558
|
1036 repository; when you prepare a repository for working with
|
bos@559
|
1037 patches using <command role="hg-ext-mq">qinit</command>, you
|
bos@559
|
1038 can pass the <option role="hg-ext-mq-cmd-qinit-opt">hg
|
bos@559
|
1039 -c</option> option to create the <filename role="special"
|
bos@558
|
1040 class="directory">.hg/patches</filename> directory as a
|
bos@558
|
1041 Mercurial repository.</para>
|
bos@558
|
1042
|
bos@558
|
1043 <note>
|
bos@558
|
1044 <para> If you forget to use the <option
|
bos@559
|
1045 role="hg-ext-mq-cmd-qinit-opt">hg -c</option> option, you
|
bos@559
|
1046 can simply go into the <filename role="special"
|
bos@558
|
1047 class="directory">.hg/patches</filename> directory at any
|
bos@559
|
1048 time and run <command role="hg-cmd">hg init</command>.
|
bos@559
|
1049 Don't forget to add an entry for the <filename
|
bos@558
|
1050 role="special">status</filename> file to the <filename
|
bos@558
|
1051 role="special">.hgignore</filename> file, though</para>
|
bos@558
|
1052
|
bos@558
|
1053 <para> (<command role="hg-cmd">hg qinit <option
|
bos@559
|
1054 role="hg-ext-mq-cmd-qinit-opt">hg -c</option></command>
|
bos@558
|
1055 does this for you automatically); you
|
bos@558
|
1056 <emphasis>really</emphasis> don't want to manage the
|
bos@558
|
1057 <filename role="special">status</filename> file.</para>
|
bos@558
|
1058 </note>
|
bos@558
|
1059
|
bos@558
|
1060 <para>As a convenience, if MQ notices that the <filename
|
bos@558
|
1061 class="directory">.hg/patches</filename> directory is a
|
bos@558
|
1062 repository, it will automatically <command role="hg-cmd">hg
|
bos@558
|
1063 add</command> every patch that you create and import.</para>
|
bos@558
|
1064
|
bos@558
|
1065 <para>MQ provides a shortcut command, <command
|
bos@559
|
1066 role="hg-ext-mq">qcommit</command>, that runs <command
|
bos@558
|
1067 role="hg-cmd">hg commit</command> in the <filename
|
bos@558
|
1068 role="special" class="directory">.hg/patches</filename>
|
bos@558
|
1069 directory. This saves some bothersome typing.</para>
|
bos@558
|
1070
|
bos@558
|
1071 <para>Finally, as a convenience to manage the patch directory,
|
bos@558
|
1072 you can define the alias <command>mq</command> on Unix
|
bos@558
|
1073 systems. For example, on Linux systems using the
|
bos@558
|
1074 <command>bash</command> shell, you can include the following
|
bos@559
|
1075 snippet in your <filename
|
bos@559
|
1076 role="home">~/.bashrc</filename>.</para>
|
bos@559
|
1077
|
bos@580
|
1078 <programlisting>alias mq=`hg -R $(hg root)/.hg/patches'</programlisting>
|
bos@558
|
1079
|
bos@558
|
1080 <para>You can then issue commands of the form <command>mq
|
bos@558
|
1081 pull</command> from the main repository.</para>
|
bos@558
|
1082
|
bos@558
|
1083 </sect2>
|
bos@558
|
1084 <sect2>
|
bos@558
|
1085 <title>A few things to watch out for</title>
|
bos@558
|
1086
|
bos@558
|
1087 <para>MQ's support for working with a repository full of patches
|
bos@558
|
1088 is limited in a few small respects.</para>
|
bos@558
|
1089
|
bos@558
|
1090 <para>MQ cannot automatically detect changes that you make to
|
bos@558
|
1091 the patch directory. If you <command role="hg-cmd">hg
|
bos@558
|
1092 pull</command>, manually edit, or <command role="hg-cmd">hg
|
bos@558
|
1093 update</command> changes to patches or the <filename
|
bos@558
|
1094 role="special">series</filename> file, you will have to
|
bos@558
|
1095 <command role="hg-cmd">hg qpop <option
|
bos@559
|
1096 role="hg-ext-mq-cmd-qpop-opt">hg -a</option></command> and
|
bos@558
|
1097 then <command role="hg-cmd">hg qpush <option
|
bos@559
|
1098 role="hg-ext-mq-cmd-qpush-opt">hg -a</option></command> in
|
bos@558
|
1099 the underlying repository to see those changes show up there.
|
bos@558
|
1100 If you forget to do this, you can confuse MQ's idea of which
|
bos@558
|
1101 patches are applied.</para>
|
bos@558
|
1102
|
bos@558
|
1103 </sect2>
|
bos@558
|
1104 </sect1>
|
dongsheng@625
|
1105 <sect1 id="sec.mq.tools">
|
bos@558
|
1106 <title>Third party tools for working with patches</title>
|
bos@558
|
1107
|
bos@558
|
1108 <para>Once you've been working with patches for a while, you'll
|
bos@558
|
1109 find yourself hungry for tools that will help you to understand
|
bos@558
|
1110 and manipulate the patches you're dealing with.</para>
|
bos@558
|
1111
|
bos@558
|
1112 <para>The <command>diffstat</command> command
|
bos@558
|
1113 <citation>web:diffstat</citation> generates a histogram of the
|
bos@558
|
1114 modifications made to each file in a patch. It provides a good
|
bos@559
|
1115 way to <quote>get a sense of</quote> a patch&emdash;which files
|
bos@559
|
1116 it affects, and how much change it introduces to each file and
|
bos@559
|
1117 as a whole. (I find that it's a good idea to use
|
bos@558
|
1118 <command>diffstat</command>'s <option
|
bos@558
|
1119 role="cmd-opt-diffstat">-p</option> option as a matter of
|
bos@558
|
1120 course, as otherwise it will try to do clever things with
|
bos@558
|
1121 prefixes of file names that inevitably confuse at least
|
bos@558
|
1122 me.)</para>
|
bos@558
|
1123
|
bos@567
|
1124 &interaction.mq.tools.tools;
|
bos@558
|
1125
|
bos@558
|
1126 <para>The <literal role="package">patchutils</literal> package
|
bos@558
|
1127 <citation>web:patchutils</citation> is invaluable. It provides a
|
bos@558
|
1128 set of small utilities that follow the <quote>Unix
|
bos@558
|
1129 philosophy;</quote> each does one useful thing with a patch.
|
bos@558
|
1130 The <literal role="package">patchutils</literal> command I use
|
bos@558
|
1131 most is <command>filterdiff</command>, which extracts subsets
|
bos@558
|
1132 from a patch file. For example, given a patch that modifies
|
bos@558
|
1133 hundreds of files across dozens of directories, a single
|
bos@558
|
1134 invocation of <command>filterdiff</command> can generate a
|
bos@558
|
1135 smaller patch that only touches files whose names match a
|
bos@558
|
1136 particular glob pattern. See section <xref
|
dongsheng@625
|
1137 linkend="mq-collab.tips.interdiff"/> for another
|
bos@558
|
1138 example.</para>
|
bos@558
|
1139
|
bos@558
|
1140 </sect1>
|
bos@558
|
1141 <sect1>
|
bos@558
|
1142 <title>Good ways to work with patches</title>
|
bos@558
|
1143
|
bos@558
|
1144 <para>Whether you are working on a patch series to submit to a
|
bos@558
|
1145 free software or open source project, or a series that you
|
bos@558
|
1146 intend to treat as a sequence of regular changesets when you're
|
bos@558
|
1147 done, you can use some simple techniques to keep your work well
|
bos@558
|
1148 organised.</para>
|
bos@558
|
1149
|
bos@558
|
1150 <para>Give your patches descriptive names. A good name for a
|
bos@558
|
1151 patch might be <filename>rework-device-alloc.patch</filename>,
|
bos@558
|
1152 because it will immediately give you a hint what the purpose of
|
bos@558
|
1153 the patch is. Long names shouldn't be a problem; you won't be
|
bos@558
|
1154 typing the names often, but you <emphasis>will</emphasis> be
|
bos@558
|
1155 running commands like <command
|
bos@559
|
1156 role="hg-ext-mq">qapplied</command> and <command
|
bos@559
|
1157 role="hg-ext-mq">qtop</command> over and over. Good naming
|
bos@558
|
1158 becomes especially important when you have a number of patches
|
bos@558
|
1159 to work with, or if you are juggling a number of different tasks
|
bos@558
|
1160 and your patches only get a fraction of your attention.</para>
|
bos@558
|
1161
|
bos@558
|
1162 <para>Be aware of what patch you're working on. Use the <command
|
bos@559
|
1163 role="hg-ext-mq">qtop</command> command and skim over the text
|
bos@558
|
1164 of your patches frequently&emdash;for example, using <command
|
bos@558
|
1165 role="hg-cmd">hg tip <option
|
bos@559
|
1166 role="hg-opt-tip">-p</option></command>)&emdash;to be sure
|
bos@559
|
1167 of where you stand. I have several times worked on and <command
|
bos@559
|
1168 role="hg-ext-mq">qrefresh</command>ed a patch other than the
|
bos@558
|
1169 one I intended, and it's often tricky to migrate changes into
|
bos@558
|
1170 the right patch after making them in the wrong one.</para>
|
bos@558
|
1171
|
bos@558
|
1172 <para>For this reason, it is very much worth investing a little
|
bos@558
|
1173 time to learn how to use some of the third-party tools I
|
dongsheng@625
|
1174 described in section <xref linkend="sec.mq.tools"/>,
|
bos@559
|
1175 particularly
|
bos@559
|
1176 <command>diffstat</command> and <command>filterdiff</command>.
|
bos@559
|
1177 The former will give you a quick idea of what changes your patch
|
bos@559
|
1178 is making, while the latter makes it easy to splice hunks
|
bos@559
|
1179 selectively out of one patch and into another.</para>
|
bos@558
|
1180
|
bos@558
|
1181 </sect1>
|
bos@558
|
1182 <sect1>
|
bos@558
|
1183 <title>MQ cookbook</title>
|
bos@558
|
1184
|
bos@558
|
1185 <sect2>
|
bos@558
|
1186 <title>Manage <quote>trivial</quote> patches</title>
|
bos@558
|
1187
|
bos@558
|
1188 <para>Because the overhead of dropping files into a new
|
bos@558
|
1189 Mercurial repository is so low, it makes a lot of sense to
|
bos@558
|
1190 manage patches this way even if you simply want to make a few
|
bos@558
|
1191 changes to a source tarball that you downloaded.</para>
|
bos@558
|
1192
|
bos@558
|
1193 <para>Begin by downloading and unpacking the source tarball, and
|
bos@567
|
1194 turning it into a Mercurial repository.</para>
|
bos@567
|
1195
|
bos@567
|
1196 &interaction.mq.tarball.download;
|
bos@558
|
1197
|
bos@558
|
1198 <para>Continue by creating a patch stack and making your
|
bos@567
|
1199 changes.</para>
|
bos@567
|
1200
|
bos@567
|
1201 &interaction.mq.tarball.qinit;
|
bos@558
|
1202
|
bos@558
|
1203 <para>Let's say a few weeks or months pass, and your package
|
bos@558
|
1204 author releases a new version. First, bring their changes
|
bos@567
|
1205 into the repository.</para>
|
bos@567
|
1206
|
bos@567
|
1207 &interaction.mq.tarball.newsource;
|
bos@567
|
1208
|
bos@567
|
1209 <para>The pipeline starting with <command role="hg-cmd">hg
|
bos@558
|
1210 locate</command> above deletes all files in the working
|
bos@558
|
1211 directory, so that <command role="hg-cmd">hg
|
bos@558
|
1212 commit</command>'s <option
|
bos@558
|
1213 role="hg-opt-commit">--addremove</option> option can
|
bos@558
|
1214 actually tell which files have really been removed in the
|
bos@558
|
1215 newer version of the source.</para>
|
bos@558
|
1216
|
bos@558
|
1217 <para>Finally, you can apply your patches on top of the new
|
bos@567
|
1218 tree.</para>
|
bos@567
|
1219
|
bos@567
|
1220 &interaction.mq.tarball.repush;
|
bos@558
|
1221
|
bos@558
|
1222 </sect2>
|
dongsheng@625
|
1223 <sect2 id="sec.mq.combine">
|
bos@558
|
1224 <title>Combining entire patches</title>
|
bos@558
|
1225
|
bos@558
|
1226 <para>MQ provides a command, <command
|
bos@559
|
1227 role="hg-ext-mq">qfold</command> that lets you combine
|
bos@558
|
1228 entire patches. This <quote>folds</quote> the patches you
|
bos@558
|
1229 name, in the order you name them, into the topmost applied
|
bos@558
|
1230 patch, and concatenates their descriptions onto the end of its
|
bos@558
|
1231 description. The patches that you fold must be unapplied
|
bos@558
|
1232 before you fold them.</para>
|
bos@558
|
1233
|
bos@558
|
1234 <para>The order in which you fold patches matters. If your
|
bos@558
|
1235 topmost applied patch is <literal>foo</literal>, and you
|
bos@559
|
1236 <command role="hg-ext-mq">qfold</command>
|
bos@558
|
1237 <literal>bar</literal> and <literal>quux</literal> into it,
|
bos@558
|
1238 you will end up with a patch that has the same effect as if
|
bos@558
|
1239 you applied first <literal>foo</literal>, then
|
bos@558
|
1240 <literal>bar</literal>, followed by
|
bos@558
|
1241 <literal>quux</literal>.</para>
|
bos@558
|
1242
|
bos@558
|
1243 </sect2>
|
bos@558
|
1244 <sect2>
|
bos@558
|
1245 <title>Merging part of one patch into another</title>
|
bos@558
|
1246
|
bos@558
|
1247 <para>Merging <emphasis>part</emphasis> of one patch into
|
bos@558
|
1248 another is more difficult than combining entire
|
bos@558
|
1249 patches.</para>
|
bos@558
|
1250
|
bos@558
|
1251 <para>If you want to move changes to entire files, you can use
|
bos@558
|
1252 <command>filterdiff</command>'s <option
|
bos@558
|
1253 role="cmd-opt-filterdiff">-i</option> and <option
|
bos@558
|
1254 role="cmd-opt-filterdiff">-x</option> options to choose the
|
bos@558
|
1255 modifications to snip out of one patch, concatenating its
|
bos@558
|
1256 output onto the end of the patch you want to merge into. You
|
bos@558
|
1257 usually won't need to modify the patch you've merged the
|
bos@558
|
1258 changes from. Instead, MQ will report some rejected hunks
|
bos@559
|
1259 when you <command role="hg-ext-mq">qpush</command> it (from
|
bos@558
|
1260 the hunks you moved into the other patch), and you can simply
|
bos@559
|
1261 <command role="hg-ext-mq">qrefresh</command> the patch to drop
|
bos@558
|
1262 the duplicate hunks.</para>
|
bos@558
|
1263
|
bos@558
|
1264 <para>If you have a patch that has multiple hunks modifying a
|
bos@558
|
1265 file, and you only want to move a few of those hunks, the job
|
bos@558
|
1266 becomes more messy, but you can still partly automate it. Use
|
bos@558
|
1267 <command>lsdiff -nvv</command> to print some metadata about
|
bos@567
|
1268 the patch.</para>
|
bos@567
|
1269
|
bos@567
|
1270 &interaction.mq.tools.lsdiff;
|
bos@558
|
1271
|
bos@558
|
1272 <para>This command prints three different kinds of
|
bos@558
|
1273 number:</para>
|
bos@558
|
1274 <itemizedlist>
|
bos@558
|
1275 <listitem><para>(in the first column) a <emphasis>file
|
bos@558
|
1276 number</emphasis> to identify each file modified in the
|
bos@559
|
1277 patch;</para>
|
bos@559
|
1278 </listitem>
|
bos@558
|
1279 <listitem><para>(on the next line, indented) the line number
|
bos@559
|
1280 within a modified file where a hunk starts; and</para>
|
bos@559
|
1281 </listitem>
|
bos@558
|
1282 <listitem><para>(on the same line) a <emphasis>hunk
|
bos@559
|
1283 number</emphasis> to identify that hunk.</para>
|
bos@559
|
1284 </listitem></itemizedlist>
|
bos@558
|
1285
|
bos@558
|
1286 <para>You'll have to use some visual inspection, and reading of
|
bos@558
|
1287 the patch, to identify the file and hunk numbers you'll want,
|
bos@558
|
1288 but you can then pass them to to
|
bos@558
|
1289 <command>filterdiff</command>'s <option
|
bos@558
|
1290 role="cmd-opt-filterdiff">--files</option> and <option
|
bos@558
|
1291 role="cmd-opt-filterdiff">--hunks</option> options, to
|
bos@558
|
1292 select exactly the file and hunk you want to extract.</para>
|
bos@558
|
1293
|
bos@558
|
1294 <para>Once you have this hunk, you can concatenate it onto the
|
bos@558
|
1295 end of your destination patch and continue with the remainder
|
dongsheng@625
|
1296 of section <xref linkend="sec.mq.combine"/>.</para>
|
bos@558
|
1297
|
bos@558
|
1298 </sect2>
|
bos@558
|
1299 </sect1>
|
bos@558
|
1300 <sect1>
|
bos@558
|
1301 <title>Differences between quilt and MQ</title>
|
bos@558
|
1302
|
bos@558
|
1303 <para>If you are already familiar with quilt, MQ provides a
|
bos@558
|
1304 similar command set. There are a few differences in the way
|
bos@558
|
1305 that it works.</para>
|
bos@558
|
1306
|
bos@558
|
1307 <para>You will already have noticed that most quilt commands have
|
bos@558
|
1308 MQ counterparts that simply begin with a
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1309 <quote><literal>q</literal></quote>. The exceptions are quilt's
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1310 <literal>add</literal> and <literal>remove</literal> commands,
|
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1311 the counterparts for which are the normal Mercurial <command
|
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1312 role="hg-cmd">hg add</command> and <command role="hg-cmd">hg
|
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1313 remove</command> commands. There is no MQ equivalent of the
|
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1314 quilt <literal>edit</literal> command.</para>
|
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1315
|
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|
1316 </sect1>
|
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1317 </chapter>
|
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|
1318
|
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|
1319 <!--
|
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|
1320 local variables:
|
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|
1321 sgml-parent-document: ("00book.xml" "book" "chapter")
|
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|
1322 end:
|
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|
1323 -->
|