hgbook

annotate en/ch02-tour-basic.xml @ 645:1114da00d30e

Fix '<programlisting>' in ch02-tour-basic.xml
author Dongsheng Song <dongsheng.song@gmail.com>
date Wed Mar 18 19:43:46 2009 +0800 (2009-03-18)
parents a13813534ccd
children d0160b0b1a9e
rev   line source
bos@553 1 <!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
bos@553 2
dongsheng@625 3 <chapter id="chap.tour-basic">
bos@572 4 <?dbhtml filename="a-tour-of-mercurial-the-basics.html"?>
bos@553 5 <title>A tour of Mercurial: the basics</title>
bos@559 6
dongsheng@625 7 <sect1 id="sec.tour.install">
bos@553 8 <title>Installing Mercurial on your system</title>
bos@553 9
bos@553 10 <para>Prebuilt binary packages of Mercurial are available for
bos@553 11 every popular operating system. These make it easy to start
bos@553 12 using Mercurial on your computer immediately.</para>
bos@553 13
bos@553 14 <sect2>
bos@553 15 <title>Linux</title>
bos@553 16
bos@553 17 <para>Because each Linux distribution has its own packaging
bos@553 18 tools, policies, and rate of development, it's difficult to
bos@553 19 give a comprehensive set of instructions on how to install
bos@553 20 Mercurial binaries. The version of Mercurial that you will
bos@553 21 end up with can vary depending on how active the person is who
bos@553 22 maintains the package for your distribution.</para>
bos@553 23
bos@553 24 <para>To keep things simple, I will focus on installing
bos@553 25 Mercurial from the command line under the most popular Linux
bos@553 26 distributions. Most of these distributions provide graphical
bos@553 27 package managers that will let you install Mercurial with a
bos@553 28 single click; the package name to look for is
bos@553 29 <literal>mercurial</literal>.</para>
bos@553 30
bos@553 31 <itemizedlist>
bos@553 32 <listitem><para>Debian:</para>
dongsheng@645 33 <programlisting>apt-get install mercurial</programlisting></listitem>
bos@553 34 <listitem><para>Fedora Core:</para>
dongsheng@645 35 <programlisting>yum install mercurial</programlisting></listitem>
bos@553 36 <listitem><para>Gentoo:</para>
bos@553 37 <programlisting>emerge mercurial</programlisting></listitem>
bos@553 38 <listitem><para>OpenSUSE:</para>
dongsheng@645 39 <programlisting>yum install mercurial</programlisting></listitem>
bos@553 40 <listitem><para>Ubuntu: Ubuntu's Mercurial package is based on
bos@553 41 Debian's. To install it, run the following
bos@553 42 command.</para>
dongsheng@645 43 <programlisting>apt-get install mercurial</programlisting></listitem>
bos@553 44 </itemizedlist>
bos@553 45
bos@553 46 </sect2>
bos@553 47 <sect2>
bos@553 48 <title>Solaris</title>
bos@553 49
bos@553 50 <para>SunFreeWare, at <ulink
bos@553 51 url="http://www.sunfreeware.com">http://www.sunfreeware.com</ulink>,
bos@553 52 is a good source for a large number of pre-built Solaris
bos@553 53 packages for 32 and 64 bit Intel and Sparc architectures,
bos@553 54 including current versions of Mercurial.</para>
bos@553 55
bos@553 56 </sect2>
bos@553 57 <sect2>
bos@553 58 <title>Mac OS X</title>
bos@553 59
bos@553 60 <para>Lee Cantey publishes an installer of Mercurial for Mac OS
bos@553 61 X at <ulink
bos@553 62 url="http://mercurial.berkwood.com">http://mercurial.berkwood.com</ulink>.
bos@559 63 This package works on both Intel- and Power-based Macs. Before
bos@559 64 you can use it, you must install a compatible version of
bos@559 65 Universal MacPython <citation>web:macpython</citation>. This
bos@559 66 is easy to do; simply follow the instructions on Lee's
bos@553 67 site.</para>
bos@553 68
bos@553 69 <para>It's also possible to install Mercurial using Fink or
bos@553 70 MacPorts, two popular free package managers for Mac OS X. If
bos@553 71 you have Fink, use <command>sudo apt-get install
bos@553 72 mercurial-py25</command>. If MacPorts, <command>sudo port
bos@553 73 install mercurial</command>.</para>
bos@553 74
bos@553 75 </sect2>
bos@553 76 <sect2>
bos@553 77 <title>Windows</title>
bos@553 78
bos@553 79 <para>Lee Cantey publishes an installer of Mercurial for Windows
bos@553 80 at <ulink
bos@553 81 url="http://mercurial.berkwood.com">http://mercurial.berkwood.com</ulink>.
bos@553 82 This package has no external dependencies; it <quote>just
bos@553 83 works</quote>.</para>
bos@553 84
bos@553 85 <note>
bos@553 86 <para> The Windows version of Mercurial does not
bos@553 87 automatically convert line endings between Windows and Unix
bos@553 88 styles. If you want to share work with Unix users, you must
bos@553 89 do a little additional configuration work. XXX Flesh this
bos@553 90 out.</para>
bos@553 91 </note>
bos@553 92
bos@553 93 </sect2>
bos@553 94 </sect1>
bos@553 95 <sect1>
bos@553 96 <title>Getting started</title>
bos@553 97
bos@553 98 <para>To begin, we'll use the <command role="hg-cmd">hg
bos@553 99 version</command> command to find out whether Mercurial is
bos@553 100 actually installed properly. The actual version information
bos@553 101 that it prints isn't so important; it's whether it prints
bos@559 102 anything at all that we care about.</para>
bos@559 103
bos@566 104 &interaction.tour.version;
bos@553 105
bos@553 106 <sect2>
bos@553 107 <title>Built-in help</title>
bos@553 108
bos@553 109 <para>Mercurial provides a built-in help system. This is
bos@559 110 invaluable for those times when you find yourself stuck
bos@559 111 trying to remember how to run a command. If you are
bos@559 112 completely stuck, simply run <command role="hg-cmd">hg
bos@559 113 help</command>; it will print a brief list of commands,
bos@559 114 along with a description of what each does. If you ask for
bos@559 115 help on a specific command (as below), it prints more
bos@559 116 detailed information.</para>
bos@559 117
bos@566 118 &interaction.tour.help;
bos@559 119
bos@559 120 <para>For a more impressive level of detail (which you won't
bos@559 121 usually need) run <command role="hg-cmd">hg help <option
bos@559 122 role="hg-opt-global">-v</option></command>. The <option
bos@559 123 role="hg-opt-global">-v</option> option is short for
bos@559 124 <option role="hg-opt-global">--verbose</option>, and tells
bos@559 125 Mercurial to print more information than it usually
bos@559 126 would.</para>
bos@553 127
bos@553 128 </sect2>
bos@553 129 </sect1>
bos@553 130 <sect1>
bos@553 131 <title>Working with a repository</title>
bos@553 132
bos@553 133 <para>In Mercurial, everything happens inside a
bos@553 134 <emphasis>repository</emphasis>. The repository for a project
bos@553 135 contains all of the files that <quote>belong to</quote> that
bos@553 136 project, along with a historical record of the project's
bos@553 137 files.</para>
bos@553 138
bos@553 139 <para>There's nothing particularly magical about a repository; it
bos@553 140 is simply a directory tree in your filesystem that Mercurial
bos@553 141 treats as special. You can rename or delete a repository any
bos@553 142 time you like, using either the command line or your file
bos@553 143 browser.</para>
bos@553 144
bos@553 145 <sect2>
bos@553 146 <title>Making a local copy of a repository</title>
bos@553 147
bos@553 148 <para><emphasis>Copying</emphasis> a repository is just a little
bos@553 149 bit special. While you could use a normal file copying
bos@553 150 command to make a copy of a repository, it's best to use a
bos@553 151 built-in command that Mercurial provides. This command is
bos@553 152 called <command role="hg-cmd">hg clone</command>, because it
bos@559 153 creates an identical copy of an existing repository.</para>
bos@559 154
bos@566 155 &interaction.tour.clone;
bos@559 156
bos@559 157 <para>If our clone succeeded, we should now have a local
bos@559 158 directory called <filename class="directory">hello</filename>.
bos@559 159 This directory will contain some files.</para>
bos@559 160
bos@566 161 &interaction.tour.ls;
bos@559 162
bos@559 163 <para>These files have the same contents and history in our
bos@559 164 repository as they do in the repository we cloned.</para>
bos@553 165
bos@553 166 <para>Every Mercurial repository is complete, self-contained,
bos@553 167 and independent. It contains its own private copy of a
bos@553 168 project's files and history. A cloned repository remembers
bos@553 169 the location of the repository it was cloned from, but it does
bos@553 170 not communicate with that repository, or any other, unless you
bos@553 171 tell it to.</para>
bos@553 172
bos@553 173 <para>What this means for now is that we're free to experiment
bos@553 174 with our repository, safe in the knowledge that it's a private
bos@553 175 <quote>sandbox</quote> that won't affect anyone else.</para>
bos@553 176
bos@553 177 </sect2>
bos@553 178 <sect2>
bos@553 179 <title>What's in a repository?</title>
bos@553 180
bos@553 181 <para>When we take a more detailed look inside a repository, we
bos@553 182 can see that it contains a directory named <filename
bos@553 183 class="directory">.hg</filename>. This is where Mercurial
bos@559 184 keeps all of its metadata for the repository.</para>
bos@559 185
bos@566 186 &interaction.tour.ls-a;
bos@553 187
bos@553 188 <para>The contents of the <filename
bos@553 189 class="directory">.hg</filename> directory and its
bos@553 190 subdirectories are private to Mercurial. Every other file and
bos@553 191 directory in the repository is yours to do with as you
bos@553 192 please.</para>
bos@553 193
bos@553 194 <para>To introduce a little terminology, the <filename
bos@553 195 class="directory">.hg</filename> directory is the
bos@553 196 <quote>real</quote> repository, and all of the files and
bos@553 197 directories that coexist with it are said to live in the
bos@553 198 <emphasis>working directory</emphasis>. An easy way to
bos@553 199 remember the distinction is that the
bos@553 200 <emphasis>repository</emphasis> contains the
bos@553 201 <emphasis>history</emphasis> of your project, while the
bos@553 202 <emphasis>working directory</emphasis> contains a
bos@553 203 <emphasis>snapshot</emphasis> of your project at a particular
bos@553 204 point in history.</para>
bos@553 205
bos@553 206 </sect2>
bos@553 207 </sect1>
bos@553 208 <sect1>
bos@553 209 <title>A tour through history</title>
bos@553 210
bos@553 211 <para>One of the first things we might want to do with a new,
bos@553 212 unfamiliar repository is understand its history. The <command
bos@553 213 role="hg-cmd">hg log</command> command gives us a view of
bos@559 214 history.</para>
bos@559 215
bos@566 216 &interaction.tour.log;
bos@559 217
bos@559 218 <para>By default, this command prints a brief paragraph of output
bos@559 219 for each change to the project that was recorded. In Mercurial
bos@559 220 terminology, we call each of these recorded events a
bos@553 221 <emphasis>changeset</emphasis>, because it can contain a record
bos@553 222 of changes to several files.</para>
bos@553 223
bos@553 224 <para>The fields in a record of output from <command
bos@553 225 role="hg-cmd">hg log</command> are as follows.</para>
bos@553 226 <itemizedlist>
bos@553 227 <listitem><para><literal>changeset</literal>: This field has the
bos@553 228 format of a number, followed by a colon, followed by a
bos@553 229 hexadecimal string. These are
bos@553 230 <emphasis>identifiers</emphasis> for the changeset. There
bos@553 231 are two identifiers because the number is shorter and easier
bos@553 232 to type than the hex string.</para></listitem>
bos@553 233 <listitem><para><literal>user</literal>: The identity of the
bos@553 234 person who created the changeset. This is a free-form
bos@553 235 field, but it most often contains a person's name and email
bos@553 236 address.</para></listitem>
bos@553 237 <listitem><para><literal>date</literal>: The date and time on
bos@553 238 which the changeset was created, and the timezone in which
bos@553 239 it was created. (The date and time are local to that
bos@553 240 timezone; they display what time and date it was for the
bos@553 241 person who created the changeset.)</para></listitem>
bos@553 242 <listitem><para><literal>summary</literal>: The first line of
bos@553 243 the text message that the creator of the changeset entered
bos@553 244 to describe the changeset.</para></listitem></itemizedlist>
bos@553 245 <para>The default output printed by <command role="hg-cmd">hg
bos@553 246 log</command> is purely a summary; it is missing a lot of
bos@553 247 detail.</para>
bos@553 248
dongsheng@640 249 <para>Figure <xref endterm="fig.tour-basic.history.caption"
dongsheng@640 250 linkend="fig.tour-basic.history"/> provides a
bos@553 251 graphical representation of the history of the <filename
bos@553 252 class="directory">hello</filename> repository, to make it a
bos@553 253 little easier to see which direction history is
bos@553 254 <quote>flowing</quote> in. We'll be returning to this figure
bos@553 255 several times in this chapter and the chapter that
bos@553 256 follows.</para>
bos@553 257
dongsheng@625 258 <informalfigure id="fig.tour-basic.history">
bos@558 259 <mediaobject>
dongsheng@625 260 <imageobject><imagedata fileref="images/tour-history.png"/></imageobject>
bos@558 261 <textobject><phrase>XXX add text</phrase></textobject>
dongsheng@640 262 <caption><para id="fig.tour-basic.history.caption">Graphical history of
dongsheng@640 263 the <filename class="directory">hello</filename> repository</para>
dongsheng@640 264 </caption>
bos@558 265 </mediaobject>
bos@558 266 </informalfigure>
bos@553 267
bos@553 268 <sect2>
bos@553 269 <title>Changesets, revisions, and talking to other
bos@553 270 people</title>
bos@553 271
bos@553 272 <para>As English is a notoriously sloppy language, and computer
bos@553 273 science has a hallowed history of terminological confusion
bos@553 274 (why use one term when four will do?), revision control has a
bos@553 275 variety of words and phrases that mean the same thing. If you
bos@553 276 are talking about Mercurial history with other people, you
bos@553 277 will find that the word <quote>changeset</quote> is often
bos@553 278 compressed to <quote>change</quote> or (when written)
bos@553 279 <quote>cset</quote>, and sometimes a changeset is referred to
bos@553 280 as a <quote>revision</quote> or a <quote>rev</quote>.</para>
bos@553 281
bos@553 282 <para>While it doesn't matter what <emphasis>word</emphasis> you
bos@553 283 use to refer to the concept of <quote>a changeset</quote>, the
bos@553 284 <emphasis>identifier</emphasis> that you use to refer to
bos@553 285 <quote>a <emphasis>specific</emphasis> changeset</quote> is of
bos@553 286 great importance. Recall that the <literal>changeset</literal>
bos@553 287 field in the output from <command role="hg-cmd">hg
bos@553 288 log</command> identifies a changeset using both a number and
bos@553 289 a hexadecimal string.</para>
bos@553 290 <itemizedlist>
bos@553 291 <listitem><para>The revision number is <emphasis>only valid in
bos@553 292 that repository</emphasis>,</para></listitem>
bos@553 293 <listitem><para>while the hex string is the
bos@553 294 <emphasis>permanent, unchanging identifier</emphasis> that
bos@553 295 will always identify that exact changeset in
bos@553 296 <emphasis>every</emphasis> copy of the
bos@553 297 repository.</para></listitem></itemizedlist>
bos@553 298 <para>This distinction is important. If you send someone an
bos@553 299 email talking about <quote>revision 33</quote>, there's a high
bos@553 300 likelihood that their revision 33 will <emphasis>not be the
bos@553 301 same</emphasis> as yours. The reason for this is that a
bos@553 302 revision number depends on the order in which changes arrived
bos@553 303 in a repository, and there is no guarantee that the same
bos@553 304 changes will happen in the same order in different
bos@553 305 repositories. Three changes $a,b,c$ can easily appear in one
bos@553 306 repository as $0,1,2$, while in another as $1,0,2$.</para>
bos@553 307
bos@553 308 <para>Mercurial uses revision numbers purely as a convenient
bos@553 309 shorthand. If you need to discuss a changeset with someone,
bos@553 310 or make a record of a changeset for some other reason (for
bos@553 311 example, in a bug report), use the hexadecimal
bos@553 312 identifier.</para>
bos@553 313
bos@553 314 </sect2>
bos@553 315 <sect2>
bos@553 316 <title>Viewing specific revisions</title>
bos@553 317
bos@553 318 <para>To narrow the output of <command role="hg-cmd">hg
bos@553 319 log</command> down to a single revision, use the <option
bos@553 320 role="hg-opt-log">-r</option> (or <option
bos@553 321 role="hg-opt-log">--rev</option>) option. You can use
bos@553 322 either a revision number or a long-form changeset identifier,
bos@559 323 and you can provide as many revisions as you want.</para>
bos@559 324
bos@566 325 &interaction.tour.log-r;
bos@553 326
bos@553 327 <para>If you want to see the history of several revisions
bos@553 328 without having to list each one, you can use <emphasis>range
bos@553 329 notation</emphasis>; this lets you express the idea <quote>I
bos@559 330 want all revisions between <literal>abc</literal> and
bos@559 331 <literal>def</literal>, inclusive</quote>.</para>
bos@559 332
bos@566 333 &interaction.tour.log.range;
bos@559 334
bos@559 335 <para>Mercurial also honours the order in which you specify
bos@559 336 revisions, so <command role="hg-cmd">hg log -r 2:4</command>
bos@559 337 prints 2, 3, and 4. while <command role="hg-cmd">hg log -r
bos@559 338 4:2</command> prints 4, 3, and 2.</para>
bos@553 339
bos@553 340 </sect2>
bos@553 341 <sect2>
bos@553 342 <title>More detailed information</title>
bos@553 343
bos@553 344 <para>While the summary information printed by <command
bos@553 345 role="hg-cmd">hg log</command> is useful if you already know
bos@553 346 what you're looking for, you may need to see a complete
bos@553 347 description of the change, or a list of the files changed, if
bos@553 348 you're trying to decide whether a changeset is the one you're
bos@553 349 looking for. The <command role="hg-cmd">hg log</command>
bos@553 350 command's <option role="hg-opt-global">-v</option> (or <option
bos@553 351 role="hg-opt-global">--verbose</option>) option gives you
bos@559 352 this extra detail.</para>
bos@559 353
bos@566 354 &interaction.tour.log-v;
bos@553 355
bos@553 356 <para>If you want to see both the description and content of a
bos@553 357 change, add the <option role="hg-opt-log">-p</option> (or
bos@553 358 <option role="hg-opt-log">--patch</option>) option. This
bos@553 359 displays the content of a change as a <emphasis>unified
bos@553 360 diff</emphasis> (if you've never seen a unified diff before,
dongsheng@625 361 see section <xref linkend="sec.mq.patch"/> for an
bos@559 362 overview).</para>
bos@559 363
bos@566 364 &interaction.tour.log-vp;
bos@553 365
bos@553 366 </sect2>
bos@553 367 </sect1>
bos@553 368 <sect1>
bos@553 369 <title>All about command options</title>
bos@553 370
bos@553 371 <para>Let's take a brief break from exploring Mercurial commands
bos@553 372 to discuss a pattern in the way that they work; you may find
bos@553 373 this useful to keep in mind as we continue our tour.</para>
bos@553 374
bos@553 375 <para>Mercurial has a consistent and straightforward approach to
bos@553 376 dealing with the options that you can pass to commands. It
bos@553 377 follows the conventions for options that are common to modern
bos@553 378 Linux and Unix systems.</para>
bos@553 379 <itemizedlist>
bos@553 380 <listitem><para>Every option has a long name. For example, as
bos@553 381 we've already seen, the <command role="hg-cmd">hg
bos@553 382 log</command> command accepts a <option
bos@553 383 role="hg-opt-log">--rev</option> option.</para></listitem>
bos@553 384 <listitem><para>Most options have short names, too. Instead of
bos@553 385 <option role="hg-opt-log">--rev</option>, we can use <option
bos@553 386 role="hg-opt-log">-r</option>. (The reason that some
bos@553 387 options don't have short names is that the options in
bos@553 388 question are rarely used.)</para></listitem>
bos@553 389 <listitem><para>Long options start with two dashes (e.g. <option
bos@553 390 role="hg-opt-log">--rev</option>), while short options
bos@553 391 start with one (e.g. <option
bos@553 392 role="hg-opt-log">-r</option>).</para></listitem>
bos@553 393 <listitem><para>Option naming and usage is consistent across
bos@553 394 commands. For example, every command that lets you specify
bos@553 395 a changeset ID or revision number accepts both <option
bos@553 396 role="hg-opt-log">-r</option> and <option
bos@553 397 role="hg-opt-log">--rev</option>
bos@553 398 arguments.</para></listitem></itemizedlist>
bos@553 399 <para>In the examples throughout this book, I use short options
bos@553 400 instead of long. This just reflects my own preference, so don't
bos@553 401 read anything significant into it.</para>
bos@553 402
bos@553 403 <para>Most commands that print output of some kind will print more
bos@553 404 output when passed a <option role="hg-opt-global">-v</option>
bos@553 405 (or <option role="hg-opt-global">--verbose</option>) option, and
bos@553 406 less when passed <option role="hg-opt-global">-q</option> (or
bos@553 407 <option role="hg-opt-global">--quiet</option>).</para>
bos@553 408
bos@553 409 </sect1>
bos@553 410 <sect1>
bos@553 411 <title>Making and reviewing changes</title>
bos@553 412
bos@553 413 <para>Now that we have a grasp of viewing history in Mercurial,
bos@553 414 let's take a look at making some changes and examining
bos@553 415 them.</para>
bos@553 416
bos@553 417 <para>The first thing we'll do is isolate our experiment in a
bos@553 418 repository of its own. We use the <command role="hg-cmd">hg
bos@553 419 clone</command> command, but we don't need to clone a copy of
bos@553 420 the remote repository. Since we already have a copy of it
bos@553 421 locally, we can just clone that instead. This is much faster
bos@553 422 than cloning over the network, and cloning a local repository
bos@559 423 uses less disk space in most cases, too.</para>
bos@559 424
bos@566 425 &interaction.tour.reclone;
bos@559 426
bos@559 427 <para>As an aside, it's often good practice to keep a
bos@559 428 <quote>pristine</quote> copy of a remote repository around,
bos@559 429 which you can then make temporary clones of to create sandboxes
bos@559 430 for each task you want to work on. This lets you work on
bos@559 431 multiple tasks in parallel, each isolated from the others until
bos@559 432 it's complete and you're ready to integrate it back. Because
bos@559 433 local clones are so cheap, there's almost no overhead to cloning
bos@559 434 and destroying repositories whenever you want.</para>
bos@553 435
bos@553 436 <para>In our <filename class="directory">my-hello</filename>
bos@553 437 repository, we have a file <filename>hello.c</filename> that
bos@553 438 contains the classic <quote>hello, world</quote> program. Let's
bos@553 439 use the ancient and venerable <command>sed</command> command to
bos@553 440 edit this file so that it prints a second line of output. (I'm
bos@553 441 only using <command>sed</command> to do this because it's easy
bos@553 442 to write a scripted example this way. Since you're not under
bos@553 443 the same constraint, you probably won't want to use
bos@553 444 <command>sed</command>; simply use your preferred text editor to
bos@559 445 do the same thing.)</para>
bos@559 446
bos@566 447 &interaction.tour.sed;
bos@553 448
bos@553 449 <para>Mercurial's <command role="hg-cmd">hg status</command>
bos@553 450 command will tell us what Mercurial knows about the files in the
bos@559 451 repository.</para>
bos@559 452
bos@566 453 &interaction.tour.status;
bos@559 454
bos@559 455 <para>The <command role="hg-cmd">hg status</command> command
bos@559 456 prints no output for some files, but a line starting with
bos@553 457 <quote><literal>M</literal></quote> for
bos@553 458 <filename>hello.c</filename>. Unless you tell it to, <command
bos@553 459 role="hg-cmd">hg status</command> will not print any output
bos@553 460 for files that have not been modified.</para>
bos@553 461
bos@553 462 <para>The <quote><literal>M</literal></quote> indicates that
bos@553 463 Mercurial has noticed that we modified
bos@553 464 <filename>hello.c</filename>. We didn't need to
bos@553 465 <emphasis>inform</emphasis> Mercurial that we were going to
bos@553 466 modify the file before we started, or that we had modified the
bos@553 467 file after we were done; it was able to figure this out
bos@553 468 itself.</para>
bos@553 469
bos@553 470 <para>It's a little bit helpful to know that we've modified
bos@553 471 <filename>hello.c</filename>, but we might prefer to know
bos@553 472 exactly <emphasis>what</emphasis> changes we've made to it. To
bos@553 473 do this, we use the <command role="hg-cmd">hg diff</command>
bos@559 474 command.</para>
bos@559 475
bos@566 476 &interaction.tour.diff;
bos@553 477
bos@553 478 </sect1>
bos@553 479 <sect1>
bos@553 480 <title>Recording changes in a new changeset</title>
bos@553 481
bos@553 482 <para>We can modify files, build and test our changes, and use
bos@553 483 <command role="hg-cmd">hg status</command> and <command
bos@553 484 role="hg-cmd">hg diff</command> to review our changes, until
bos@553 485 we're satisfied with what we've done and arrive at a natural
bos@553 486 stopping point where we want to record our work in a new
bos@553 487 changeset.</para>
bos@553 488
bos@553 489 <para>The <command role="hg-cmd">hg commit</command> command lets
bos@553 490 us create a new changeset; we'll usually refer to this as
bos@553 491 <quote>making a commit</quote> or
bos@553 492 <quote>committing</quote>.</para>
bos@553 493
bos@553 494 <sect2>
bos@553 495 <title>Setting up a username</title>
bos@553 496
bos@553 497 <para>When you try to run <command role="hg-cmd">hg
bos@553 498 commit</command> for the first time, it is not guaranteed to
bos@553 499 succeed. Mercurial records your name and address with each
bos@553 500 change that you commit, so that you and others will later be
bos@553 501 able to tell who made each change. Mercurial tries to
bos@553 502 automatically figure out a sensible username to commit the
bos@553 503 change with. It will attempt each of the following methods,
bos@553 504 in order:</para>
bos@553 505 <orderedlist>
bos@553 506 <listitem><para>If you specify a <option
bos@553 507 role="hg-opt-commit">-u</option> option to the <command
bos@553 508 role="hg-cmd">hg commit</command> command on the command
bos@553 509 line, followed by a username, this is always given the
bos@553 510 highest precedence.</para></listitem>
bos@553 511 <listitem><para>If you have set the <envar>HGUSER</envar>
bos@553 512 environment variable, this is checked
bos@553 513 next.</para></listitem>
bos@553 514 <listitem><para>If you create a file in your home directory
bos@553 515 called <filename role="special">.hgrc</filename>, with a
bos@553 516 <envar role="rc-item-ui">username</envar> entry, that will
bos@553 517 be used next. To see what the contents of this file
bos@553 518 should look like, refer to section <xref
dongsheng@625 519 linkend="sec.tour-basic.username"/>
bos@553 520 below.</para></listitem>
bos@553 521 <listitem><para>If you have set the <envar>EMAIL</envar>
bos@553 522 environment variable, this will be used
bos@553 523 next.</para></listitem>
bos@553 524 <listitem><para>Mercurial will query your system to find out
bos@553 525 your local user name and host name, and construct a
bos@553 526 username from these components. Since this often results
bos@553 527 in a username that is not very useful, it will print a
bos@553 528 warning if it has to do
bos@558 529 this.</para></listitem>
bos@558 530 </orderedlist>
bos@558 531 <para>If all of these mechanisms fail, Mercurial will
bos@553 532 fail, printing an error message. In this case, it will not
bos@553 533 let you commit until you set up a
bos@558 534 username.</para>
bos@558 535 <para>You should think of the <envar>HGUSER</envar> environment
bos@558 536 variable and the <option role="hg-opt-commit">-u</option>
bos@558 537 option to the <command role="hg-cmd">hg commit</command>
bos@558 538 command as ways to <emphasis>override</emphasis> Mercurial's
bos@558 539 default selection of username. For normal use, the simplest
bos@558 540 and most robust way to set a username for yourself is by
bos@558 541 creating a <filename role="special">.hgrc</filename> file; see
bos@558 542 below for details.</para>
dongsheng@625 543 <sect3 id="sec.tour-basic.username">
bos@553 544 <title>Creating a Mercurial configuration file</title>
bos@558 545
bos@558 546 <para>To set a user name, use your favourite editor
bos@553 547 to create a file called <filename
bos@553 548 role="special">.hgrc</filename> in your home directory.
bos@553 549 Mercurial will use this file to look up your personalised
bos@553 550 configuration settings. The initial contents of your
bos@553 551 <filename role="special">.hgrc</filename> should look like
bos@558 552 this.</para>
bos@558 553 <programlisting># This is a Mercurial configuration file.
bos@558 554 [ui] username = Firstname Lastname
bos@558 555 &lt;email.address@domain.net&gt;</programlisting>
bos@558 556
bos@558 557 <para>The <quote><literal>[ui]</literal></quote> line begins a
bos@558 558 <emphasis>section</emphasis> of the config file, so you can
bos@558 559 read the <quote><literal>username = ...</literal></quote>
bos@558 560 line as meaning <quote>set the value of the
bos@558 561 <literal>username</literal> item in the
bos@558 562 <literal>ui</literal> section</quote>. A section continues
bos@558 563 until a new section begins, or the end of the file.
bos@558 564 Mercurial ignores empty lines and treats any text from
bos@558 565 <quote><literal>#</literal></quote> to the end of a line as
bos@558 566 a comment.</para>
bos@553 567 </sect3>
bos@558 568
bos@553 569 <sect3>
bos@553 570 <title>Choosing a user name</title>
bos@553 571
bos@558 572 <para>You can use any text you like as the value of
bos@553 573 the <literal>username</literal> config item, since this
bos@553 574 information is for reading by other people, but for
bos@553 575 interpreting by Mercurial. The convention that most
bos@553 576 people follow is to use their name and email address, as
bos@558 577 in the example above.</para>
bos@553 578 <note>
bos@558 579 <para>Mercurial's built-in web server obfuscates
bos@553 580 email addresses, to make it more difficult for the email
bos@553 581 harvesting tools that spammers use. This reduces the
bos@553 582 likelihood that you'll start receiving more junk email
bos@553 583 if you publish a Mercurial repository on the
bos@558 584 web.</para></note>
bos@553 585
bos@553 586 </sect3>
bos@553 587 </sect2>
bos@553 588 <sect2>
bos@553 589 <title>Writing a commit message</title>
bos@553 590
bos@558 591 <para>When we commit a change, Mercurial drops us into
bos@553 592 a text editor, to enter a message that will describe the
bos@553 593 modifications we've made in this changeset. This is called
bos@553 594 the <emphasis>commit message</emphasis>. It will be a
bos@553 595 record for readers of what we did and why, and it will be
bos@553 596 printed by <command role="hg-cmd">hg log</command> after
bos@558 597 we've finished committing.</para>
bos@558 598
bos@566 599 &interaction.tour.commit;
bos@558 600
bos@558 601 <para>The editor that the <command role="hg-cmd">hg
bos@553 602 commit</command> command drops us into will contain an
bos@553 603 empty line, followed by a number of lines starting with
bos@558 604 <quote><literal>HG:</literal></quote>.</para>
bos@558 605
bos@558 606 <programlisting>XXX fix this XXX</programlisting>
bos@558 607
bos@558 608 <para>Mercurial ignores the lines that start with
bos@553 609 <quote><literal>HG:</literal></quote>; it uses them only to
bos@553 610 tell us which files it's recording changes to. Modifying or
bos@558 611 deleting these lines has no effect.</para>
bos@553 612 </sect2>
bos@553 613 <sect2>
bos@553 614 <title>Writing a good commit message</title>
bos@553 615
bos@558 616 <para>Since <command role="hg-cmd">hg log</command>
bos@553 617 only prints the first line of a commit message by default,
bos@553 618 it's best to write a commit message whose first line stands
bos@553 619 alone. Here's a real example of a commit message that
bos@553 620 <emphasis>doesn't</emphasis> follow this guideline, and
bos@553 621 hence has a summary that is not
bos@558 622 readable.</para>
bos@558 623
bos@558 624 <programlisting>
bos@558 625 changeset: 73:584af0e231be
bos@558 626 user: Censored Person &lt;censored.person@example.org&gt;
bos@558 627 date: Tue Sep 26 21:37:07 2006 -0700
bos@558 628 summary: include buildmeister/commondefs. Add exports.</programlisting>
bos@558 629
bos@558 630 <para>As far as the remainder of the contents of the
bos@553 631 commit message are concerned, there are no hard-and-fast
bos@553 632 rules. Mercurial itself doesn't interpret or care about the
bos@553 633 contents of the commit message, though your project may have
bos@553 634 policies that dictate a certain kind of
bos@558 635 formatting.</para>
bos@558 636 <para>My personal preference is for short, but
bos@553 637 informative, commit messages that tell me something that I
bos@553 638 can't figure out with a quick glance at the output of
bos@553 639 <command role="hg-cmd">hg log
bos@558 640 --patch</command>.</para>
bos@553 641 </sect2>
bos@553 642 <sect2>
bos@553 643 <title>Aborting a commit</title>
bos@553 644
bos@558 645 <para>If you decide that you don't want to commit
bos@553 646 while in the middle of editing a commit message, simply exit
bos@553 647 from your editor without saving the file that it's editing.
bos@553 648 This will cause nothing to happen to either the repository
bos@558 649 or the working directory.</para>
bos@558 650 <para>If we run the <command role="hg-cmd">hg
bos@553 651 commit</command> command without any arguments, it records
bos@553 652 all of the changes we've made, as reported by <command
bos@553 653 role="hg-cmd">hg status</command> and <command
bos@558 654 role="hg-cmd">hg diff</command>.</para>
bos@553 655 </sect2>
bos@553 656 <sect2>
bos@553 657 <title>Admiring our new handiwork</title>
bos@553 658
bos@558 659 <para>Once we've finished the commit, we can use the
bos@553 660 <command role="hg-cmd">hg tip</command> command to display
bos@553 661 the changeset we just created. This command produces output
bos@553 662 that is identical to <command role="hg-cmd">hg
bos@553 663 log</command>, but it only displays the newest revision in
bos@558 664 the repository.</para>
bos@558 665
bos@566 666 &interaction.tour.tip;
bos@558 667
bos@558 668 <para>We refer to
bos@553 669 the newest revision in the repository as the tip revision,
bos@558 670 or simply the tip.</para>
bos@553 671 </sect2>
bos@553 672 </sect1>
bos@558 673
bos@553 674 <sect1>
bos@553 675 <title>Sharing changes</title>
bos@553 676
bos@558 677 <para>We mentioned earlier that repositories in
bos@553 678 Mercurial are self-contained. This means that the changeset
bos@553 679 we just created exists only in our <filename
bos@553 680 class="directory">my-hello</filename> repository. Let's
bos@553 681 look at a few ways that we can propagate this change into
bos@558 682 other repositories.</para>
bos@558 683
dongsheng@625 684 <sect2 id="sec.tour.pull">
bos@553 685 <title>Pulling changes from another repository</title>
bos@558 686 <para>To get started, let's clone our original
bos@553 687 <filename class="directory">hello</filename> repository,
bos@553 688 which does not contain the change we just committed. We'll
bos@553 689 call our temporary repository <filename
bos@558 690 class="directory">hello-pull</filename>.</para>
bos@558 691
bos@566 692 &interaction.tour.clone-pull;
bos@558 693
bos@558 694 <para>We'll use the <command role="hg-cmd">hg
bos@553 695 pull</command> command to bring changes from <filename
bos@553 696 class="directory">my-hello</filename> into <filename
bos@553 697 class="directory">hello-pull</filename>. However, blindly
bos@553 698 pulling unknown changes into a repository is a somewhat
bos@553 699 scary prospect. Mercurial provides the <command
bos@553 700 role="hg-cmd">hg incoming</command> command to tell us
bos@553 701 what changes the <command role="hg-cmd">hg pull</command>
bos@553 702 command <emphasis>would</emphasis> pull into the repository,
bos@558 703 without actually pulling the changes in.</para>
bos@558 704
bos@566 705 &interaction.tour.incoming;
bos@558 706
bos@558 707 <para>(Of course, someone could
bos@553 708 cause more changesets to appear in the repository that we
bos@553 709 ran <command role="hg-cmd">hg incoming</command> in, before
bos@553 710 we get a chance to <command role="hg-cmd">hg pull</command>
bos@553 711 the changes, so that we could end up pulling changes that we
bos@558 712 didn't expect.)</para>
bos@558 713
bos@558 714 <para>Bringing changes into a repository is a simple
bos@553 715 matter of running the <command role="hg-cmd">hg
bos@553 716 pull</command> command, and telling it which repository to
bos@558 717 pull from.</para>
bos@558 718
bos@566 719 &interaction.tour.pull;
bos@558 720
bos@558 721 <para>As you can see
bos@553 722 from the before-and-after output of <command
bos@553 723 role="hg-cmd">hg tip</command>, we have successfully
bos@553 724 pulled changes into our repository. There remains one step
bos@553 725 before we can see these changes in the working
bos@558 726 directory.</para>
bos@553 727 </sect2>
bos@553 728 <sect2>
bos@553 729 <title>Updating the working directory</title>
bos@553 730
bos@559 731 <para>We have so far glossed over the relationship between a
bos@559 732 repository and its working directory. The <command
bos@559 733 role="hg-cmd">hg pull</command> command that we ran in
dongsheng@625 734 section <xref linkend="sec.tour.pull"/> brought changes
bos@559 735 into the repository, but if we check, there's no sign of those
bos@559 736 changes in the working directory. This is because <command
bos@559 737 role="hg-cmd">hg pull</command> does not (by default) touch
bos@559 738 the working directory. Instead, we use the <command
bos@559 739 role="hg-cmd">hg update</command> command to do this.</para>
bos@559 740
bos@566 741 &interaction.tour.update;
bos@559 742
bos@559 743 <para>It might seem a bit strange that <command role="hg-cmd">hg
bos@559 744 pull</command> doesn't update the working directory
bos@559 745 automatically. There's actually a good reason for this: you
bos@559 746 can use <command role="hg-cmd">hg update</command> to update
bos@559 747 the working directory to the state it was in at <emphasis>any
bos@559 748 revision</emphasis> in the history of the repository. If
bos@559 749 you had the working directory updated to an old revision---to
bos@559 750 hunt down the origin of a bug, say---and ran a <command
bos@559 751 role="hg-cmd">hg pull</command> which automatically updated
bos@559 752 the working directory to a new revision, you might not be
bos@559 753 terribly happy.</para>
bos@559 754 <para>However, since pull-then-update is such a common thing to
bos@559 755 do, Mercurial lets you combine the two by passing the <option
bos@559 756 role="hg-opt-pull">-u</option> option to <command
bos@559 757 role="hg-cmd">hg pull</command>.</para>
bos@558 758
bos@558 759 <para>If you look back at the output of <command
bos@559 760 role="hg-cmd">hg pull</command> in section <xref
dongsheng@625 761 linkend="sec.tour.pull"/> when we ran it without <option
bos@559 762 role="hg-opt-pull">-u</option>, you can see that it printed
bos@559 763 a helpful reminder that we'd have to take an explicit step to
bos@559 764 update the working directory:</para>
bos@558 765
bos@558 766 <!-- &interaction.xxx.fixme; -->
bos@558 767
bos@559 768 <para>To find out what revision the working directory is at, use
bos@559 769 the <command role="hg-cmd">hg parents</command>
bos@559 770 command.</para>
bos@558 771
bos@566 772 &interaction.tour.parents;
bos@558 773
bos@559 774 <para>If you look back at figure <xref
dongsheng@640 775 endterm="fig.tour-basic.history.caption"
dongsheng@640 776 linkend="fig.tour-basic.history"/>,
bos@559 777 you'll see arrows connecting each changeset. The node that
bos@559 778 the arrow leads <emphasis>from</emphasis> in each case is a
bos@559 779 parent, and the node that the arrow leads
bos@559 780 <emphasis>to</emphasis> is its child. The working directory
bos@559 781 has a parent in just the same way; this is the changeset that
bos@559 782 the working directory currently contains.</para>
bos@559 783
bos@559 784 <para>To update the working directory to a particular revision,
bos@559 785
bos@559 786 give a revision number or changeset ID to the <command
bos@559 787 role="hg-cmd">hg update</command> command.</para>
bos@559 788
bos@566 789 &interaction.tour.older;
bos@559 790
bos@559 791 <para>If you omit an explicit revision, <command
bos@559 792 role="hg-cmd">hg update</command> will update to the tip
bos@559 793 revision, as shown by the second call to <command
bos@559 794 role="hg-cmd">hg update</command> in the example
bos@559 795 above.</para>
bos@558 796 </sect2>
bos@558 797
bos@553 798 <sect2>
bos@553 799 <title>Pushing changes to another repository</title>
bos@553 800
bos@558 801 <para>Mercurial lets us push changes to another
bos@553 802 repository, from the repository we're currently visiting.
bos@553 803 As with the example of <command role="hg-cmd">hg
bos@553 804 pull</command> above, we'll create a temporary repository
bos@558 805 to push our changes into.</para>
bos@558 806
bos@566 807 &interaction.tour.clone-push;
bos@558 808
bos@558 809 <para>The <command role="hg-cmd">hg outgoing</command> command
bos@553 810 tells us what changes would be pushed into another
bos@558 811 repository.</para>
bos@558 812
bos@566 813 &interaction.tour.outgoing;
bos@558 814
bos@558 815 <para>And the
bos@553 816 <command role="hg-cmd">hg push</command> command does the
bos@558 817 actual push.</para>
bos@558 818
bos@566 819 &interaction.tour.push;
bos@558 820
bos@558 821 <para>As with
bos@553 822 <command role="hg-cmd">hg pull</command>, the <command
bos@553 823 role="hg-cmd">hg push</command> command does not update
bos@553 824 the working directory in the repository that it's pushing
bos@553 825 changes into. (Unlike <command role="hg-cmd">hg
bos@553 826 pull</command>, <command role="hg-cmd">hg push</command>
bos@553 827 does not provide a <literal>-u</literal> option that updates
bos@558 828 the other repository's working directory.)</para>
bos@558 829
bos@558 830 <para>What happens if we try to pull or push changes
bos@553 831 and the receiving repository already has those changes?
bos@558 832 Nothing too exciting.</para>
bos@558 833
bos@566 834 &interaction.tour.push.nothing;
bos@553 835 </sect2>
bos@553 836 <sect2>
bos@553 837 <title>Sharing changes over a network</title>
bos@553 838
bos@558 839 <para>The commands we have covered in the previous few
bos@553 840 sections are not limited to working with local repositories.
bos@553 841 Each works in exactly the same fashion over a network
bos@558 842 connection; simply pass in a URL instead of a local
bos@558 843 path.</para>
bos@558 844
bos@566 845 &interaction.tour.outgoing.net;
bos@558 846
bos@558 847 <para>In this example, we
bos@553 848 can see what changes we could push to the remote repository,
bos@553 849 but the repository is understandably not set up to let
bos@558 850 anonymous users push to it.</para>
bos@558 851
bos@566 852 &interaction.tour.push.net;
bos@553 853 </sect2>
bos@553 854 </sect1>
bos@553 855 </chapter>
bos@553 856
bos@553 857 <!--
bos@553 858 local variables:
bos@553 859 sgml-parent-document: ("00book.xml" "book" "chapter")
bos@553 860 end:
bos@553 861 -->