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annotate en/ch07-filenames.xml @ 568:a8160b8a4f15

Add 2009 copyright year
author Bryan O'Sullivan <bos@serpentine.com>
date Mon Mar 09 23:22:57 2009 -0700 (2009-03-09)
parents 21c62e09b99f
children 13513d2a128d
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bos@559 1 <!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
bos@559 2
bos@559 3 <chapter id="chap:names">
bos@559 4 <title>File names and pattern matching</title>
bos@559 5
bos@559 6 <para>Mercurial provides mechanisms that let you work with file
bos@559 7 names in a consistent and expressive way.</para>
bos@559 8
bos@559 9 <sect1>
bos@559 10 <title>Simple file naming</title>
bos@559 11
bos@559 12 <para>Mercurial uses a unified piece of machinery <quote>under the
bos@559 13 hood</quote> to handle file names. Every command behaves
bos@559 14 uniformly with respect to file names. The way in which commands
bos@559 15 work with file names is as follows.</para>
bos@559 16
bos@559 17 <para>If you explicitly name real files on the command line,
bos@559 18 Mercurial works with exactly those files, as you would expect.
bos@567 19 &interaction.filenames.files;</para>
bos@559 20
bos@559 21 <para>When you provide a directory name, Mercurial will interpret
bos@559 22 this as <quote>operate on every file in this directory and its
bos@559 23 subdirectories</quote>. Mercurial traverses the files and
bos@559 24 subdirectories in a directory in alphabetical order. When it
bos@559 25 encounters a subdirectory, it will traverse that subdirectory
bos@567 26 before continuing with the current directory.</para>
bos@567 27
bos@567 28 &interaction.filenames.dirs;
bos@559 29
bos@559 30 </sect1>
bos@559 31 <sect1>
bos@559 32 <title>Running commands without any file names</title>
bos@559 33
bos@559 34 <para>Mercurial's commands that work with file names have useful
bos@559 35 default behaviours when you invoke them without providing any
bos@559 36 file names or patterns. What kind of behaviour you should
bos@559 37 expect depends on what the command does. Here are a few rules
bos@559 38 of thumb you can use to predict what a command is likely to do
bos@559 39 if you don't give it any names to work with.</para>
bos@559 40 <itemizedlist>
bos@559 41 <listitem><para>Most commands will operate on the entire working
bos@559 42 directory. This is what the <command role="hg-cmd">hg
bos@559 43 add</command> command does, for example.</para>
bos@559 44 </listitem>
bos@559 45 <listitem><para>If the command has effects that are difficult or
bos@559 46 impossible to reverse, it will force you to explicitly
bos@559 47 provide at least one name or pattern (see below). This
bos@559 48 protects you from accidentally deleting files by running
bos@559 49 <command role="hg-cmd">hg remove</command> with no
bos@559 50 arguments, for example.</para>
bos@559 51 </listitem></itemizedlist>
bos@559 52
bos@559 53 <para>It's easy to work around these default behaviours if they
bos@559 54 don't suit you. If a command normally operates on the whole
bos@559 55 working directory, you can invoke it on just the current
bos@559 56 directory and its subdirectories by giving it the name
bos@567 57 <quote><filename class="directory">.</filename></quote>.</para>
bos@567 58
bos@567 59 &interaction.filenames.wdir-subdir;
bos@559 60
bos@559 61 <para>Along the same lines, some commands normally print file
bos@559 62 names relative to the root of the repository, even if you're
bos@559 63 invoking them from a subdirectory. Such a command will print
bos@559 64 file names relative to your subdirectory if you give it explicit
bos@559 65 names. Here, we're going to run <command role="hg-cmd">hg
bos@559 66 status</command> from a subdirectory, and get it to operate on
bos@559 67 the entire working directory while printing file names relative
bos@559 68 to our subdirectory, by passing it the output of the <command
bos@567 69 role="hg-cmd">hg root</command> command.</para>
bos@567 70
bos@567 71 &interaction.filenames.wdir-relname;
bos@559 72
bos@559 73 </sect1>
bos@559 74 <sect1>
bos@559 75 <title>Telling you what's going on</title>
bos@559 76
bos@559 77 <para>The <command role="hg-cmd">hg add</command> example in the
bos@559 78 preceding section illustrates something else that's helpful
bos@559 79 about Mercurial commands. If a command operates on a file that
bos@559 80 you didn't name explicitly on the command line, it will usually
bos@559 81 print the name of the file, so that you will not be surprised
bos@559 82 what's going on.</para>
bos@559 83
bos@559 84 <para>The principle here is of <emphasis>least
bos@559 85 surprise</emphasis>. If you've exactly named a file on the
bos@559 86 command line, there's no point in repeating it back at you. If
bos@559 87 Mercurial is acting on a file <emphasis>implicitly</emphasis>,
bos@559 88 because you provided no names, or a directory, or a pattern (see
bos@559 89 below), it's safest to tell you what it's doing.</para>
bos@559 90
bos@559 91 <para>For commands that behave this way, you can silence them
bos@559 92 using the <option role="hg-opt-global">-q</option> option. You
bos@559 93 can also get them to print the name of every file, even those
bos@559 94 you've named explicitly, using the <option
bos@559 95 role="hg-opt-global">-v</option> option.</para>
bos@559 96
bos@559 97 </sect1>
bos@559 98 <sect1>
bos@559 99 <title>Using patterns to identify files</title>
bos@559 100
bos@559 101 <para>In addition to working with file and directory names,
bos@559 102 Mercurial lets you use <emphasis>patterns</emphasis> to identify
bos@559 103 files. Mercurial's pattern handling is expressive.</para>
bos@559 104
bos@559 105 <para>On Unix-like systems (Linux, MacOS, etc.), the job of
bos@559 106 matching file names to patterns normally falls to the shell. On
bos@559 107 these systems, you must explicitly tell Mercurial that a name is
bos@559 108 a pattern. On Windows, the shell does not expand patterns, so
bos@559 109 Mercurial will automatically identify names that are patterns,
bos@559 110 and expand them for you.</para>
bos@559 111
bos@559 112 <para>To provide a pattern in place of a regular name on the
bos@559 113 command line, the mechanism is simple:</para>
bos@559 114 <programlisting>syntax:patternbody</programlisting>
bos@559 115 <para>That is, a pattern is identified by a short text string that
bos@559 116 says what kind of pattern this is, followed by a colon, followed
bos@559 117 by the actual pattern.</para>
bos@559 118
bos@559 119 <para>Mercurial supports two kinds of pattern syntax. The most
bos@559 120 frequently used is called <literal>glob</literal>; this is the
bos@559 121 same kind of pattern matching used by the Unix shell, and should
bos@559 122 be familiar to Windows command prompt users, too.</para>
bos@559 123
bos@559 124 <para>When Mercurial does automatic pattern matching on Windows,
bos@559 125 it uses <literal>glob</literal> syntax. You can thus omit the
bos@559 126 <quote><literal>glob:</literal></quote> prefix on Windows, but
bos@559 127 it's safe to use it, too.</para>
bos@559 128
bos@559 129 <para>The <literal>re</literal> syntax is more powerful; it lets
bos@559 130 you specify patterns using regular expressions, also known as
bos@559 131 regexps.</para>
bos@559 132
bos@559 133 <para>By the way, in the examples that follow, notice that I'm
bos@559 134 careful to wrap all of my patterns in quote characters, so that
bos@559 135 they won't get expanded by the shell before Mercurial sees
bos@559 136 them.</para>
bos@559 137
bos@559 138 <sect2>
bos@559 139 <title>Shell-style <literal>glob</literal> patterns</title>
bos@559 140
bos@559 141 <para>This is an overview of the kinds of patterns you can use
bos@559 142 when you're matching on glob patterns.</para>
bos@559 143
bos@559 144 <para>The <quote><literal>*</literal></quote> character matches
bos@567 145 any string, within a single directory.</para>
bos@567 146
bos@567 147 &interaction.filenames.glob.star;
bos@559 148
bos@559 149 <para>The <quote><literal>**</literal></quote> pattern matches
bos@559 150 any string, and crosses directory boundaries. It's not a
bos@559 151 standard Unix glob token, but it's accepted by several popular
bos@567 152 Unix shells, and is very useful.</para>
bos@567 153
bos@567 154 &interaction.filenames.glob.starstar;
bos@559 155
bos@559 156 <para>The <quote><literal>?</literal></quote> pattern matches
bos@567 157 any single character.</para>
bos@567 158
bos@567 159 &interaction.filenames.glob.question;
bos@559 160
bos@559 161 <para>The <quote><literal>[</literal></quote> character begins a
bos@559 162 <emphasis>character class</emphasis>. This matches any single
bos@559 163 character within the class. The class ends with a
bos@559 164 <quote><literal>]</literal></quote> character. A class may
bos@559 165 contain multiple <emphasis>range</emphasis>s of the form
bos@559 166 <quote><literal>a-f</literal></quote>, which is shorthand for
bos@567 167 <quote><literal>abcdef</literal></quote>.</para>
bos@567 168
bos@567 169 &interaction.filenames.glob.range;
bos@567 170
bos@567 171 <para>If the first character after the
bos@567 172 <quote><literal>[</literal></quote> in a character class is a
bos@567 173 <quote><literal>!</literal></quote>, it
bos@559 174 <emphasis>negates</emphasis> the class, making it match any
bos@559 175 single character not in the class.</para>
bos@559 176
bos@559 177 <para>A <quote><literal>{</literal></quote> begins a group of
bos@559 178 subpatterns, where the whole group matches if any subpattern
bos@559 179 in the group matches. The <quote><literal>,</literal></quote>
bos@567 180 character separates subpatterns, and
bos@567 181 <quote><literal>}</literal></quote> ends the group.</para>
bos@567 182
bos@567 183 &interaction.filenames.glob.group;
bos@559 184
bos@559 185 <sect3>
bos@559 186 <title>Watch out!</title>
bos@559 187
bos@559 188 <para>Don't forget that if you want to match a pattern in any
bos@559 189 directory, you should not be using the
bos@559 190 <quote><literal>*</literal></quote> match-any token, as this
bos@559 191 will only match within one directory. Instead, use the
bos@559 192 <quote><literal>**</literal></quote> token. This small
bos@567 193 example illustrates the difference between the two.</para>
bos@567 194
bos@567 195 &interaction.filenames.glob.star-starstar;
bos@559 196
bos@559 197 </sect3>
bos@559 198 </sect2>
bos@559 199 <sect2>
bos@559 200 <title>Regular expression matching with <literal>re</literal>
bos@559 201 patterns</title>
bos@559 202
bos@559 203 <para>Mercurial accepts the same regular expression syntax as
bos@559 204 the Python programming language (it uses Python's regexp
bos@559 205 engine internally). This is based on the Perl language's
bos@559 206 regexp syntax, which is the most popular dialect in use (it's
bos@559 207 also used in Java, for example).</para>
bos@559 208
bos@559 209 <para>I won't discuss Mercurial's regexp dialect in any detail
bos@559 210 here, as regexps are not often used. Perl-style regexps are
bos@559 211 in any case already exhaustively documented on a multitude of
bos@559 212 web sites, and in many books. Instead, I will focus here on a
bos@559 213 few things you should know if you find yourself needing to use
bos@559 214 regexps with Mercurial.</para>
bos@559 215
bos@559 216 <para>A regexp is matched against an entire file name, relative
bos@559 217 to the root of the repository. In other words, even if you're
bos@559 218 already in subbdirectory <filename
bos@559 219 class="directory">foo</filename>, if you want to match files
bos@559 220 under this directory, your pattern must start with
bos@559 221 <quote><literal>foo/</literal></quote>.</para>
bos@559 222
bos@559 223 <para>One thing to note, if you're familiar with Perl-style
bos@559 224 regexps, is that Mercurial's are <emphasis>rooted</emphasis>.
bos@559 225 That is, a regexp starts matching against the beginning of a
bos@559 226 string; it doesn't look for a match anywhere within the
bos@559 227 string. To match anywhere in a string, start your pattern
bos@559 228 with <quote><literal>.*</literal></quote>.</para>
bos@559 229
bos@559 230 </sect2>
bos@559 231 </sect1>
bos@559 232 <sect1>
bos@559 233 <title>Filtering files</title>
bos@559 234
bos@559 235 <para>Not only does Mercurial give you a variety of ways to
bos@559 236 specify files; it lets you further winnow those files using
bos@559 237 <emphasis>filters</emphasis>. Commands that work with file
bos@559 238 names accept two filtering options.</para>
bos@559 239 <itemizedlist>
bos@559 240 <listitem><para><option role="hg-opt-global">-I</option>, or
bos@559 241 <option role="hg-opt-global">--include</option>, lets you
bos@559 242 specify a pattern that file names must match in order to be
bos@559 243 processed.</para>
bos@559 244 </listitem>
bos@559 245 <listitem><para><option role="hg-opt-global">-X</option>, or
bos@559 246 <option role="hg-opt-global">--exclude</option>, gives you a
bos@559 247 way to <emphasis>avoid</emphasis> processing files, if they
bos@559 248 match this pattern.</para>
bos@559 249 </listitem></itemizedlist>
bos@559 250 <para>You can provide multiple <option
bos@559 251 role="hg-opt-global">-I</option> and <option
bos@559 252 role="hg-opt-global">-X</option> options on the command line,
bos@559 253 and intermix them as you please. Mercurial interprets the
bos@559 254 patterns you provide using glob syntax by default (but you can
bos@559 255 use regexps if you need to).</para>
bos@559 256
bos@559 257 <para>You can read a <option role="hg-opt-global">-I</option>
bos@559 258 filter as <quote>process only the files that match this
bos@567 259 filter</quote>.</para>
bos@567 260
bos@567 261 &interaction.filenames.filter.include;
bos@567 262
bos@567 263 <para>The <option role="hg-opt-global">-X</option> filter is best
bos@559 264 read as <quote>process only the files that don't match this
bos@567 265 pattern</quote>.</para>
bos@567 266
bos@567 267 &interaction.filenames.filter.exclude;
bos@559 268
bos@559 269 </sect1>
bos@559 270 <sect1>
bos@559 271 <title>Ignoring unwanted files and directories</title>
bos@559 272
bos@559 273 <para>XXX.</para>
bos@559 274
bos@559 275 </sect1>
bos@559 276 <sect1 id="sec:names:case">
bos@559 277 <title>Case sensitivity</title>
bos@559 278
bos@559 279 <para>If you're working in a mixed development environment that
bos@559 280 contains both Linux (or other Unix) systems and Macs or Windows
bos@559 281 systems, you should keep in the back of your mind the knowledge
bos@559 282 that they treat the case (<quote>N</quote> versus
bos@559 283 <quote>n</quote>) of file names in incompatible ways. This is
bos@559 284 not very likely to affect you, and it's easy to deal with if it
bos@559 285 does, but it could surprise you if you don't know about
bos@559 286 it.</para>
bos@559 287
bos@559 288 <para>Operating systems and filesystems differ in the way they
bos@559 289 handle the <emphasis>case</emphasis> of characters in file and
bos@559 290 directory names. There are three common ways to handle case in
bos@559 291 names.</para>
bos@559 292 <itemizedlist>
bos@559 293 <listitem><para>Completely case insensitive. Uppercase and
bos@559 294 lowercase versions of a letter are treated as identical,
bos@559 295 both when creating a file and during subsequent accesses.
bos@559 296 This is common on older DOS-based systems.</para>
bos@559 297 </listitem>
bos@559 298 <listitem><para>Case preserving, but insensitive. When a file
bos@559 299 or directory is created, the case of its name is stored, and
bos@559 300 can be retrieved and displayed by the operating system.
bos@559 301 When an existing file is being looked up, its case is
bos@559 302 ignored. This is the standard arrangement on Windows and
bos@559 303 MacOS. The names <filename>foo</filename> and
bos@559 304 <filename>FoO</filename> identify the same file. This
bos@559 305 treatment of uppercase and lowercase letters as
bos@559 306 interchangeable is also referred to as <emphasis>case
bos@559 307 folding</emphasis>.</para>
bos@559 308 </listitem>
bos@559 309 <listitem><para>Case sensitive. The case of a name is
bos@559 310 significant at all times. The names <filename>foo</filename>
bos@559 311 and {FoO} identify different files. This is the way Linux
bos@559 312 and Unix systems normally work.</para>
bos@559 313 </listitem></itemizedlist>
bos@559 314
bos@559 315 <para>On Unix-like systems, it is possible to have any or all of
bos@559 316 the above ways of handling case in action at once. For example,
bos@559 317 if you use a USB thumb drive formatted with a FAT32 filesystem
bos@559 318 on a Linux system, Linux will handle names on that filesystem in
bos@559 319 a case preserving, but insensitive, way.</para>
bos@559 320
bos@559 321 <sect2>
bos@559 322 <title>Safe, portable repository storage</title>
bos@559 323
bos@559 324 <para>Mercurial's repository storage mechanism is <emphasis>case
bos@559 325 safe</emphasis>. It translates file names so that they can
bos@559 326 be safely stored on both case sensitive and case insensitive
bos@559 327 filesystems. This means that you can use normal file copying
bos@559 328 tools to transfer a Mercurial repository onto, for example, a
bos@559 329 USB thumb drive, and safely move that drive and repository
bos@559 330 back and forth between a Mac, a PC running Windows, and a
bos@559 331 Linux box.</para>
bos@559 332
bos@559 333 </sect2>
bos@559 334 <sect2>
bos@559 335 <title>Detecting case conflicts</title>
bos@559 336
bos@559 337 <para>When operating in the working directory, Mercurial honours
bos@559 338 the naming policy of the filesystem where the working
bos@559 339 directory is located. If the filesystem is case preserving,
bos@559 340 but insensitive, Mercurial will treat names that differ only
bos@559 341 in case as the same.</para>
bos@559 342
bos@559 343 <para>An important aspect of this approach is that it is
bos@559 344 possible to commit a changeset on a case sensitive (typically
bos@559 345 Linux or Unix) filesystem that will cause trouble for users on
bos@559 346 case insensitive (usually Windows and MacOS) users. If a
bos@559 347 Linux user commits changes to two files, one named
bos@559 348 <filename>myfile.c</filename> and the other named
bos@559 349 <filename>MyFile.C</filename>, they will be stored correctly
bos@559 350 in the repository. And in the working directories of other
bos@559 351 Linux users, they will be correctly represented as separate
bos@559 352 files.</para>
bos@559 353
bos@559 354 <para>If a Windows or Mac user pulls this change, they will not
bos@559 355 initially have a problem, because Mercurial's repository
bos@559 356 storage mechanism is case safe. However, once they try to
bos@559 357 <command role="hg-cmd">hg update</command> the working
bos@559 358 directory to that changeset, or <command role="hg-cmd">hg
bos@559 359 merge</command> with that changeset, Mercurial will spot the
bos@559 360 conflict between the two file names that the filesystem would
bos@559 361 treat as the same, and forbid the update or merge from
bos@559 362 occurring.</para>
bos@559 363
bos@559 364 </sect2>
bos@559 365 <sect2>
bos@559 366 <title>Fixing a case conflict</title>
bos@559 367
bos@559 368 <para>If you are using Windows or a Mac in a mixed environment
bos@559 369 where some of your collaborators are using Linux or Unix, and
bos@559 370 Mercurial reports a case folding conflict when you try to
bos@559 371 <command role="hg-cmd">hg update</command> or <command
bos@559 372 role="hg-cmd">hg merge</command>, the procedure to fix the
bos@559 373 problem is simple.</para>
bos@559 374
bos@559 375 <para>Just find a nearby Linux or Unix box, clone the problem
bos@559 376 repository onto it, and use Mercurial's <command
bos@559 377 role="hg-cmd">hg rename</command> command to change the
bos@559 378 names of any offending files or directories so that they will
bos@559 379 no longer cause case folding conflicts. Commit this change,
bos@559 380 <command role="hg-cmd">hg pull</command> or <command
bos@559 381 role="hg-cmd">hg push</command> it across to your Windows or
bos@559 382 MacOS system, and <command role="hg-cmd">hg update</command>
bos@559 383 to the revision with the non-conflicting names.</para>
bos@559 384
bos@559 385 <para>The changeset with case-conflicting names will remain in
bos@559 386 your project's history, and you still won't be able to
bos@559 387 <command role="hg-cmd">hg update</command> your working
bos@559 388 directory to that changeset on a Windows or MacOS system, but
bos@559 389 you can continue development unimpeded.</para>
bos@559 390
bos@559 391 <note>
bos@559 392 <para> Prior to version 0.9.3, Mercurial did not use a case
bos@559 393 safe repository storage mechanism, and did not detect case
bos@559 394 folding conflicts. If you are using an older version of
bos@559 395 Mercurial on Windows or MacOS, I strongly recommend that you
bos@559 396 upgrade.</para>
bos@559 397 </note>
bos@559 398
bos@559 399 </sect2>
bos@559 400 </sect1>
bos@559 401 </chapter>
bos@559 402
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