bos@559: <!-- vim: set filetype=docbkxml shiftwidth=2 autoindent expandtab tw=77 : -->
bos@559: 
dongsheng@625: <chapter id="chap.daily">
bos@572:   <?dbhtml filename="mercurial-in-daily-use.html"?>
bos@559:   <title>Mercurial in daily use</title>
bos@559: 
bos@559:   <sect1>
bos@559:     <title>Telling Mercurial which files to track</title>
bos@559: 
bos@559:     <para>Mercurial does not work with files in your repository unless
bos@559:       you tell it to manage them.  The <command role="hg-cmd">hg
bos@559: 	status</command> command will tell you which files Mercurial
bos@559:       doesn't know about; it uses a
bos@559:       <quote><literal>?</literal></quote> to display such
bos@559:       files.</para>
bos@559: 
bos@559:     <para>To tell Mercurial to track a file, use the <command
bos@559: 	role="hg-cmd">hg add</command> command.  Once you have added a
bos@559:       file, the entry in the output of <command role="hg-cmd">hg
bos@559: 	status</command> for that file changes from
bos@559:       <quote><literal>?</literal></quote> to
bos@567:       <quote><literal>A</literal></quote>.</para>
bos@567: 
bos@567:       &interaction.daily.files.add;
bos@559: 
bos@559:     <para>After you run a <command role="hg-cmd">hg commit</command>,
bos@559:       the files that you added before the commit will no longer be
bos@559:       listed in the output of <command role="hg-cmd">hg
bos@559: 	status</command>.  The reason for this is that <command
bos@559: 	role="hg-cmd">hg status</command> only tells you about
bos@559:       <quote>interesting</quote> files&emdash;those that you have
bos@559:       modified or told Mercurial to do something with&emdash;by
bos@559:       default.  If you have a repository that contains thousands of
bos@559:       files, you will rarely want to know about files that Mercurial
bos@559:       is tracking, but that have not changed.  (You can still get this
bos@559:       information; we'll return to this later.)</para>
bos@559: 
bos@559:     <para>Once you add a file, Mercurial doesn't do anything with it
bos@559:       immediately.  Instead, it will take a snapshot of the file's
bos@559:       state the next time you perform a commit.  It will then continue
bos@559:       to track the changes you make to the file every time you commit,
bos@559:       until you remove the file.</para>
bos@559: 
bos@559:     <sect2>
bos@559:       <title>Explicit versus implicit file naming</title>
bos@559: 
bos@559:       <para>A useful behaviour that Mercurial has is that if you pass
bos@559: 	the name of a directory to a command, every Mercurial command
bos@559: 	will treat this as <quote>I want to operate on every file in
bos@567: 	  this directory and its subdirectories</quote>.</para>
bos@567: 
bos@567:       &interaction.daily.files.add-dir;
bos@567: 
bos@567:       <para>Notice in this example that Mercurial printed the names of
bos@567: 	the files it added, whereas it didn't do so when we added the
bos@567: 	file named <filename>a</filename> in the earlier
bos@567: 	example.</para>
bos@559: 
bos@559:       <para>What's going on is that in the former case, we explicitly
bos@559: 	named the file to add on the command line, so the assumption
bos@559: 	that Mercurial makes in such cases is that you know what you
bos@559: 	were doing, and it doesn't print any output.</para>
bos@559: 
bos@559:       <para>However, when we <emphasis>imply</emphasis> the names of
bos@559: 	files by giving the name of a directory, Mercurial takes the
bos@559: 	extra step of printing the name of each file that it does
bos@559: 	something with.  This makes it more clear what is happening,
bos@559: 	and reduces the likelihood of a silent and nasty surprise.
bos@559: 	This behaviour is common to most Mercurial commands.</para>
bos@559: 
bos@559:     </sect2>
bos@559:     <sect2>
bos@559:       <title>Aside: Mercurial tracks files, not directories</title>
bos@559: 
bos@559:       <para>Mercurial does not track directory information.  Instead,
bos@559: 	it tracks the path to a file.  Before creating a file, it
bos@559: 	first creates any missing directory components of the path.
bos@559: 	After it deletes a file, it then deletes any empty directories
bos@559: 	that were in the deleted file's path.  This sounds like a
bos@559: 	trivial distinction, but it has one minor practical
bos@559: 	consequence: it is not possible to represent a completely
bos@559: 	empty directory in Mercurial.</para>
bos@559: 
bos@559:       <para>Empty directories are rarely useful, and there are
bos@559: 	unintrusive workarounds that you can use to achieve an
bos@559: 	appropriate effect.  The developers of Mercurial thus felt
bos@559: 	that the complexity that would be required to manage empty
bos@559: 	directories was not worth the limited benefit this feature
bos@559: 	would bring.</para>
bos@559: 
bos@559:       <para>If you need an empty directory in your repository, there
bos@559: 	are a few ways to achieve this. One is to create a directory,
bos@559: 	then <command role="hg-cmd">hg add</command> a
bos@559: 	<quote>hidden</quote> file to that directory.  On Unix-like
bos@559: 	systems, any file name that begins with a period
bos@559: 	(<quote><literal>.</literal></quote>) is treated as hidden by
bos@559: 	most commands and GUI tools.  This approach is illustrated
bos@559: 	below.</para>
bos@559: 
bos@567: &interaction.daily.files.hidden;
bos@559: 
bos@559:       <para>Another way to tackle a need for an empty directory is to
bos@559: 	simply create one in your automated build scripts before they
bos@559: 	will need it.</para>
bos@559: 
bos@559:     </sect2>
bos@559:   </sect1>
bos@559:   <sect1>
bos@559:     <title>How to stop tracking a file</title>
bos@559: 
bos@559:     <para>Once you decide that a file no longer belongs in your
bos@559:       repository, use the <command role="hg-cmd">hg remove</command>
bos@559:       command; this deletes the file, and tells Mercurial to stop
bos@559:       tracking it.  A removed file is represented in the output of
bos@559:       <command role="hg-cmd">hg status</command> with a
bos@567:       <quote><literal>R</literal></quote>.</para>
bos@567: 
bos@567:     &interaction.daily.files.remove;
bos@559: 
bos@559:     <para>After you <command role="hg-cmd">hg remove</command> a file,
bos@559:       Mercurial will no longer track changes to that file, even if you
bos@559:       recreate a file with the same name in your working directory.
bos@559:       If you do recreate a file with the same name and want Mercurial
bos@559:       to track the new file, simply <command role="hg-cmd">hg
bos@559: 	add</command> it. Mercurial will know that the newly added
bos@559:       file is not related to the old file of the same name.</para>
bos@559: 
bos@559:     <sect2>
bos@559:       <title>Removing a file does not affect its history</title>
bos@559: 
bos@559:       <para>It is important to understand that removing a file has
bos@559: 	only two effects.</para>
bos@559:       <itemizedlist>
bos@559: 	<listitem><para>It removes the current version of the file
bos@559: 	    from the working directory.</para>
bos@559: 	</listitem>
bos@559: 	<listitem><para>It stops Mercurial from tracking changes to
bos@559: 	    the file, from the time of the next commit.</para>
bos@559: 	</listitem></itemizedlist>
bos@559:       <para>Removing a file <emphasis>does not</emphasis> in any way
bos@559: 	alter the <emphasis>history</emphasis> of the file.</para>
bos@559: 
bos@559:       <para>If you update the working directory to a changeset in
bos@559: 	which a file that you have removed was still tracked, it will
bos@559: 	reappear in the working directory, with the contents it had
bos@559: 	when you committed that changeset.  If you then update the
bos@559: 	working directory to a later changeset, in which the file had
bos@559: 	been removed, Mercurial will once again remove the file from
bos@559: 	the working directory.</para>
bos@559: 
bos@559:     </sect2>
bos@559:     <sect2>
bos@559:       <title>Missing files</title>
bos@559: 
bos@559:       <para>Mercurial considers a file that you have deleted, but not
bos@559: 	used <command role="hg-cmd">hg remove</command> to delete, to
bos@559: 	be <emphasis>missing</emphasis>.  A missing file is
bos@559: 	represented with <quote><literal>!</literal></quote> in the
bos@559: 	output of <command role="hg-cmd">hg status</command>.
bos@559: 	Mercurial commands will not generally do anything with missing
bos@567: 	files.</para>
bos@567: 
bos@567:       &interaction.daily.files.missing;
bos@559: 
bos@559:       <para>If your repository contains a file that <command
bos@559: 	  role="hg-cmd">hg status</command> reports as missing, and
bos@559: 	you want the file to stay gone, you can run <command
bos@559: 	  role="hg-cmd">hg remove <option
bos@559: 	    role="hg-opt-remove">--after</option></command> at any
bos@559: 	time later on, to tell Mercurial that you really did mean to
bos@567: 	remove the file.</para>
bos@567: 
bos@567:       &interaction.daily.files.remove-after;
bos@559: 
bos@559:       <para>On the other hand, if you deleted the missing file by
bos@559: 	accident, give <command role="hg-cmd">hg revert</command> the
bos@559: 	name of the file to recover.  It will reappear, in unmodified
bos@559: 	form.</para>
bos@559: 
bos@567: &interaction.daily.files.recover-missing;
bos@559: 
bos@559:     </sect2>
bos@559:     <sect2>
bos@559:       <title>Aside: why tell Mercurial explicitly to remove a
bos@559: 	file?</title>
bos@559: 
bos@559:       <para>You might wonder why Mercurial requires you to explicitly
bos@559: 	tell it that you are deleting a file.  Early during the
bos@559: 	development of Mercurial, it let you delete a file however you
bos@559: 	pleased; Mercurial would notice the absence of the file
bos@559: 	automatically when you next ran a <command role="hg-cmd">hg
bos@559: 	  commit</command>, and stop tracking the file.  In practice,
bos@559: 	this made it too easy to accidentally remove a file without
bos@559: 	noticing.</para>
bos@559: 
bos@559:     </sect2>
bos@559:     <sect2>
bos@559:       <title>Useful shorthand&emdash;adding and removing files in one
bos@559: 	step</title>
bos@559: 
bos@559:       <para>Mercurial offers a combination command, <command
bos@559: 	  role="hg-cmd">hg addremove</command>, that adds untracked
bos@567: 	files and marks missing files as removed.</para>
bos@567: 
bos@567:       &interaction.daily.files.addremove;
bos@567: 
bos@567:       <para>The <command role="hg-cmd">hg commit</command> command
bos@567: 	also provides a <option role="hg-opt-commit">-A</option>
bos@567: 	option that performs this same add-and-remove, immediately
bos@567: 	followed by a commit.</para>
bos@567: 
bos@567:       &interaction.daily.files.commit-addremove;
bos@559: 
bos@559:     </sect2>
bos@559:   </sect1>
bos@559:   <sect1>
bos@559:     <title>Copying files</title>
bos@559: 
bos@559:     <para>Mercurial provides a <command role="hg-cmd">hg
bos@559: 	copy</command> command that lets you make a new copy of a
bos@559:       file.  When you copy a file using this command, Mercurial makes
bos@559:       a record of the fact that the new file is a copy of the original
bos@559:       file.  It treats these copied files specially when you merge
bos@559:       your work with someone else's.</para>
bos@559: 
bos@559:     <sect2>
bos@559:       <title>The results of copying during a merge</title>
bos@559: 
bos@559:       <para>What happens during a merge is that changes
bos@559: 	<quote>follow</quote> a copy.  To best illustrate what this
bos@559: 	means, let's create an example.  We'll start with the usual
bos@567: 	tiny repository that contains a single file.</para>
bos@567: 
bos@567:       &interaction.daily.copy.init;
bos@567: 
bos@567:       <para>We need to do some work in
bos@559: 	parallel, so that we'll have something to merge.  So let's
bos@567: 	clone our repository.</para>
bos@567: 
bos@567:       &interaction.daily.copy.clone;
bos@567: 
bos@567:       <para>Back in our initial repository, let's use the <command
bos@559: 	  role="hg-cmd">hg copy</command> command to make a copy of
bos@567: 	the first file we created.</para>
bos@567: 
bos@567:       &interaction.daily.copy.copy;
bos@559: 
bos@559:       <para>If we look at the output of the <command role="hg-cmd">hg
bos@559: 	  status</command> command afterwards, the copied file looks
bos@567: 	just like a normal added file.</para>
bos@567: 
bos@567:       &interaction.daily.copy.status;
bos@567: 
bos@567:       <para>But if we pass the <option
bos@559: 	  role="hg-opt-status">-C</option> option to <command
bos@559: 	  role="hg-cmd">hg status</command>, it prints another line of
bos@559: 	output: this is the file that our newly-added file was copied
bos@567: 	<emphasis>from</emphasis>.</para>
bos@567: 
bos@567:       &interaction.daily.copy.status-copy;
bos@559: 
bos@559:       <para>Now, back in the repository we cloned, let's make a change
bos@559: 	in parallel.  We'll add a line of content to the original file
bos@567: 	that we created.</para>
bos@567: 
bos@567:       &interaction.daily.copy.other;
bos@567: 
bos@567:       <para>Now we have a modified <filename>file</filename> in this
bos@559: 	repository.  When we pull the changes from the first
bos@559: 	repository, and merge the two heads, Mercurial will propagate
bos@559: 	the changes that we made locally to <filename>file</filename>
bos@567: 	into its copy, <filename>new-file</filename>.</para>
bos@567: 
bos@567:       &interaction.daily.copy.merge;
bos@559: 
bos@559:     </sect2>
dongsheng@625:     <sect2 id="sec.daily.why-copy">
bos@559:       <title>Why should changes follow copies?</title>
bos@559: 
bos@559:       <para>This behaviour, of changes to a file propagating out to
bos@559: 	copies of the file, might seem esoteric, but in most cases
bos@559: 	it's highly desirable.</para>
bos@559: 
bos@559:       <para>First of all, remember that this propagation
bos@559: 	<emphasis>only</emphasis> happens when you merge.  So if you
bos@559: 	<command role="hg-cmd">hg copy</command> a file, and
bos@559: 	subsequently modify the original file during the normal course
bos@559: 	of your work, nothing will happen.</para>
bos@559: 
bos@559:       <para>The second thing to know is that modifications will only
bos@559: 	propagate across a copy as long as the repository that you're
bos@559: 	pulling changes from <emphasis>doesn't know</emphasis> about
bos@559: 	the copy.</para>
bos@559: 
bos@559:       <para>The reason that Mercurial does this is as follows.  Let's
bos@559: 	say I make an important bug fix in a source file, and commit
bos@559: 	my changes. Meanwhile, you've decided to <command
bos@559: 	  role="hg-cmd">hg copy</command> the file in your repository,
bos@559: 	without knowing about the bug or having seen the fix, and you
bos@559: 	have started hacking on your copy of the file.</para>
bos@559: 
bos@559:       <para>If you pulled and merged my changes, and Mercurial
bos@559: 	<emphasis>didn't</emphasis> propagate changes across copies,
bos@559: 	your source file would now contain the bug, and unless you
bos@559: 	remembered to propagate the bug fix by hand, the bug would
bos@559: 	<emphasis>remain</emphasis> in your copy of the file.</para>
bos@559: 
bos@559:       <para>By automatically propagating the change that fixed the bug
bos@559: 	from the original file to the copy, Mercurial prevents this
bos@559: 	class of problem. To my knowledge, Mercurial is the
bos@559: 	<emphasis>only</emphasis> revision control system that
bos@559: 	propagates changes across copies like this.</para>
bos@559: 
bos@559:       <para>Once your change history has a record that the copy and
bos@559: 	subsequent merge occurred, there's usually no further need to
bos@559: 	propagate changes from the original file to the copied file,
bos@559: 	and that's why Mercurial only propagates changes across copies
bos@559: 	until this point, and no further.</para>
bos@559: 
bos@559:     </sect2>
bos@559:     <sect2>
bos@559:       <title>How to make changes <emphasis>not</emphasis> follow a
bos@559: 	copy</title>
bos@559: 
bos@559:       <para>If, for some reason, you decide that this business of
bos@559: 	automatically propagating changes across copies is not for
bos@559: 	you, simply use your system's normal file copy command (on
bos@559: 	Unix-like systems, that's <command>cp</command>) to make a
bos@559: 	copy of a file, then <command role="hg-cmd">hg add</command>
bos@559: 	the new copy by hand.  Before you do so, though, please do
dongsheng@625: 	reread section <xref linkend="sec.daily.why-copy"/>, and make
bos@559: 	an informed
bos@559: 	decision that this behaviour is not appropriate to your
bos@559: 	specific case.</para>
bos@559: 
bos@559:     </sect2>
bos@559:     <sect2>
bos@559:       <title>Behaviour of the <command role="hg-cmd">hg copy</command>
bos@559: 	command</title>
bos@559: 
bos@559:       <para>When you use the <command role="hg-cmd">hg copy</command>
bos@559: 	command, Mercurial makes a copy of each source file as it
bos@559: 	currently stands in the working directory.  This means that if
bos@559: 	you make some modifications to a file, then <command
bos@559: 	  role="hg-cmd">hg copy</command> it without first having
bos@559: 	committed those changes, the new copy will also contain the
bos@559: 	modifications you have made up until that point.  (I find this
bos@559: 	behaviour a little counterintuitive, which is why I mention it
bos@559: 	here.)</para>
bos@559: 
bos@559:       <para>The <command role="hg-cmd">hg copy</command> command acts
bos@559: 	similarly to the Unix <command>cp</command> command (you can
bos@559: 	use the <command role="hg-cmd">hg cp</command> alias if you
bos@559: 	prefer).  The last argument is the
bos@559: 	<emphasis>destination</emphasis>, and all prior arguments are
bos@559: 	<emphasis>sources</emphasis>.  If you pass it a single file as
bos@559: 	the source, and the destination does not exist, it creates a
bos@567: 	new file with that name.</para>
bos@567: 
bos@567:       &interaction.daily.copy.simple;
bos@567:       
bos@567:       <para>If the destination is a directory, Mercurial copies its
bos@567: 	sources into that directory.</para>
bos@567: 
bos@567:       &interaction.daily.copy.dir-dest;
bos@567: 
bos@567:       <para>Copying a directory is
bos@559: 	recursive, and preserves the directory structure of the
bos@567: 	source.</para>
bos@567: 
bos@567:       &interaction.daily.copy.dir-src;
bos@567: 
bos@567:       <para>If the source and destination are both directories, the
bos@567: 	source tree is recreated in the destination directory.</para>
bos@567: 
bos@567: 	&interaction.daily.copy.dir-src-dest;
bos@559: 
bos@559:       <para>As with the <command role="hg-cmd">hg rename</command>
bos@559: 	command, if you copy a file manually and then want Mercurial
bos@559: 	to know that you've copied the file, simply use the <option
bos@559: 	  role="hg-opt-copy">--after</option> option to <command
bos@567: 	  role="hg-cmd">hg copy</command>.</para>
bos@567: 
bos@567:       &interaction.daily.copy.after;
bos@559: 
bos@559:     </sect2>
bos@559:   </sect1>
bos@559:   <sect1>
bos@559:     <title>Renaming files</title>
bos@559: 
bos@559:     <para>It's rather more common to need to rename a file than to
bos@559:       make a copy of it.  The reason I discussed the <command
bos@559: 	role="hg-cmd">hg copy</command> command before talking about
bos@559:       renaming files is that Mercurial treats a rename in essentially
bos@559:       the same way as a copy.  Therefore, knowing what Mercurial does
bos@559:       when you copy a file tells you what to expect when you rename a
bos@559:       file.</para>
bos@559: 
bos@559:     <para>When you use the <command role="hg-cmd">hg rename</command>
bos@559:       command, Mercurial makes a copy of each source file, then
bos@567:       deletes it and marks the file as removed.</para>
bos@567: 
bos@567:       &interaction.daily.rename.rename;
bos@567: 
bos@567:     <para>The <command role="hg-cmd">hg status</command> command shows
bos@567:       the newly copied file as added, and the copied-from file as
bos@567:       removed.</para>
bos@567: 
bos@567:     &interaction.daily.rename.status;
bos@567: 
bos@567:     <para>As with the results of a <command role="hg-cmd">hg
bos@567: 	copy</command>, we must use the <option
bos@567: 	role="hg-opt-status">-C</option> option to <command
bos@559: 	role="hg-cmd">hg status</command> to see that the added file
bos@559:       is really being tracked by Mercurial as a copy of the original,
bos@567:       now removed, file.</para>
bos@567: 
bos@567:     &interaction.daily.rename.status-copy;
bos@559: 
bos@559:     <para>As with <command role="hg-cmd">hg remove</command> and
bos@559:       <command role="hg-cmd">hg copy</command>, you can tell Mercurial
bos@559:       about a rename after the fact using the <option
bos@559: 	role="hg-opt-rename">--after</option> option.  In most other
bos@559:       respects, the behaviour of the <command role="hg-cmd">hg
bos@559: 	rename</command> command, and the options it accepts, are
bos@559:       similar to the <command role="hg-cmd">hg copy</command>
bos@559:       command.</para>
bos@559: 
bos@559:     <sect2>
bos@559:       <title>Renaming files and merging changes</title>
bos@559: 
bos@559:       <para>Since Mercurial's rename is implemented as
bos@559: 	copy-and-remove, the same propagation of changes happens when
bos@559: 	you merge after a rename as after a copy.</para>
bos@559: 
bos@559:       <para>If I modify a file, and you rename it to a new name, and
bos@559: 	then we merge our respective changes, my modifications to the
bos@559: 	file under its original name will be propagated into the file
bos@559: 	under its new name. (This is something you might expect to
bos@559: 	<quote>simply work,</quote> but not all revision control
bos@559: 	systems actually do this.)</para>
bos@559: 
bos@559:       <para>Whereas having changes follow a copy is a feature where
bos@559: 	you can perhaps nod and say <quote>yes, that might be
bos@559: 	  useful,</quote> it should be clear that having them follow a
bos@559: 	rename is definitely important.  Without this facility, it
bos@559: 	would simply be too easy for changes to become orphaned when
bos@559: 	files are renamed.</para>
bos@559: 
bos@559:     </sect2>
bos@559:     <sect2>
bos@559:       <title>Divergent renames and merging</title>
bos@559: 
bos@559:       <para>The case of diverging names occurs when two developers
bos@559: 	start with a file&emdash;let's call it
bos@559: 	<filename>foo</filename>&emdash;in their respective
bos@559: 	repositories.</para>
bos@559: 
bos@567:       &interaction.rename.divergent.clone;
bos@567: 
bos@567:       <para>Anne renames the file to <filename>bar</filename>.</para>
bos@567: 
bos@567:       &interaction.rename.divergent.rename.anne;
bos@567: 
bos@567:       <para>Meanwhile, Bob renames it to
bos@567: 	<filename>quux</filename>.</para>
bos@567: 
bos@567: 	&interaction.rename.divergent.rename.bob;
bos@559: 
bos@559:       <para>I like to think of this as a conflict because each
bos@559: 	developer has expressed different intentions about what the
bos@559: 	file ought to be named.</para>
bos@559: 
bos@559:       <para>What do you think should happen when they merge their
bos@559: 	work? Mercurial's actual behaviour is that it always preserves
bos@559: 	<emphasis>both</emphasis> names when it merges changesets that
bos@567: 	contain divergent renames.</para>
bos@567: 
bos@567:       &interaction.rename.divergent.merge;
bos@559: 
bos@559:       <para>Notice that Mercurial does warn about the divergent
bos@559: 	renames, but it leaves it up to you to do something about the
bos@559: 	divergence after the merge.</para>
bos@559: 
bos@559:     </sect2>
bos@559:     <sect2>
bos@559:       <title>Convergent renames and merging</title>
bos@559: 
bos@559:       <para>Another kind of rename conflict occurs when two people
bos@559: 	choose to rename different <emphasis>source</emphasis> files
bos@559: 	to the same <emphasis>destination</emphasis>. In this case,
bos@559: 	Mercurial runs its normal merge machinery, and lets you guide
bos@559: 	it to a suitable resolution.</para>
bos@559: 
bos@559:     </sect2>
bos@559:     <sect2>
bos@559:       <title>Other name-related corner cases</title>
bos@559: 
bos@559:       <para>Mercurial has a longstanding bug in which it fails to
bos@559: 	handle a merge where one side has a file with a given name,
bos@559: 	while another has a directory with the same name.  This is
bos@559: 	documented as <ulink role="hg-bug"
bos@559: 	  url="http://www.selenic.com/mercurial/bts/issue29">issue
bos@567: 	  29</ulink>.</para>
bos@567: 
bos@567:       &interaction.issue29.go;
bos@559: 
bos@559:     </sect2>
bos@559:   </sect1>
bos@559:   <sect1>
bos@559:     <title>Recovering from mistakes</title>
bos@559: 
bos@559:     <para>Mercurial has some useful commands that will help you to
bos@559:       recover from some common mistakes.</para>
bos@559: 
bos@559:     <para>The <command role="hg-cmd">hg revert</command> command lets
bos@559:       you undo changes that you have made to your working directory.
bos@559:       For example, if you <command role="hg-cmd">hg add</command> a
bos@559:       file by accident, just run <command role="hg-cmd">hg
bos@559: 	revert</command> with the name of the file you added, and
bos@559:       while the file won't be touched in any way, it won't be tracked
bos@559:       for adding by Mercurial any longer, either.  You can also use
bos@559:       <command role="hg-cmd">hg revert</command> to get rid of
bos@559:       erroneous changes to a file.</para>
bos@559: 
bos@559:     <para>It's useful to remember that the <command role="hg-cmd">hg
bos@559: 	revert</command> command is useful for changes that you have
bos@559:       not yet committed.  Once you've committed a change, if you
bos@559:       decide it was a mistake, you can still do something about it,
bos@559:       though your options may be more limited.</para>
bos@559: 
bos@559:     <para>For more information about the <command role="hg-cmd">hg
bos@559: 	revert</command> command, and details about how to deal with
bos@559:       changes you have already committed, see chapter <xref
dongsheng@625: 	linkend="chap.undo"/>.</para>
bos@559: 
bos@559:   </sect1>
bos@559: </chapter>
bos@559: 
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