<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sect1 SYSTEM "../../../dtd/dblite.dtd">
<sect1 id="tsvn-dug-patch">
	<title>Creating and Applying Patches</title>
	<indexterm>
		<primary>patch</primary>
	</indexterm>
	<indexterm>
		<primary>diff</primary>
	</indexterm>
	<indexterm>
		<primary>unified diff</primary>
	</indexterm>
	<?dbhh topicname="HIDD_PATCH"?>
	<?dbhh topicname="HIDD_CREATEPATCH"?>
	<para>
		For open source projects (like this one) everyone has read
		access to the repository, and anyone can make a contribution
		to the project. So how are those contributions controlled?
		If just anyone could commit changes, the project would be permanently
		unstable and probably permanently broken. In this situation the
		change is managed by submitting a <firstterm>patch</firstterm> file
		to the development team, who do have write access.
		They can review the patch first, and then either submit it to the
		repository or reject it back to the author.
	</para>
	<para>
		Patch files are simply Unified-Diff files showing the differences
		between your working copy and the base revision.
	</para>
	<sect2 id="tsvn-dug-patch-1">
		<title>Creating a Patch File</title>
		<para>
			First you need to make <emphasis>and test</emphasis> your changes.
			Then instead of using
			<menuchoice>
				<guimenu>TortoiseGit</guimenu>
				<guimenuitem>Commit...</guimenuitem>
			</menuchoice>
			on the parent folder, you select
			<menuchoice>
				<guimenu>TortoiseGit</guimenu>
				<guimenuitem>Create Patch...</guimenuitem>
			</menuchoice>
		</para>
		<figure id="tsvn-dug-patch-dia-1">
			<title>The Create Patch dialog</title>
			<graphic fileref="../images/CreatePatch.png"/>
		</figure>
		<para>
			you can now select the files you want included in the patch,
			just as you would with a full commit. This will produce a single
			file containing a summary of all the changes you have made to the
			selected files since the last update from the repository.
		</para>
		<para>
			The columns in this dialog can be customized in the same way as the
			columns in the <guilabel>Check for modifications</guilabel> dialog.
			Read <xref linkend="tsvn-dug-wcstatus-2"/> for further details.
		</para>
		<para>
			You can produce separate patches containing changes to different
			sets of files. Of course, if you create a patch file, make some more changes
			to the <emphasis>same</emphasis> files and then create another patch, the
			second patch file will include <emphasis>both</emphasis> sets of changes.
		</para>
		<para>
			Just save the file using a filename of your choice.
			Patch files can have any extension you like, but by convention they
			should use the <filename>.patch</filename> or
			<filename>.diff</filename> extension.
			You are now ready to submit your patch file.
		</para>
		<para>
			You can also save the patch to the clipboard instead of to a file.
			You might want to do this so that you can paste it into an email for
			review by others. Or if you have two working copies on one machine and
			you want to transfer changes from one to the other, a patch on the
			clipboard is a convenient way of doing this.
		</para>
	</sect2>
	<sect2 id="tsvn-dug-patch-2">
		<title>Applying a Patch File</title>
		<para>
			Patch files are applied to your working copy. This should be done
			from the same folder level as was used to create the patch.
			If you are not sure what this is, just look at the first line of
			the patch file. For example, if the first file being worked on was
			<filename>doc/source/english/chapter1.xml</filename>
			and the first line in the patch file is
			<filename>Index: english/chapter1.xml</filename>
			then you need to apply the patch to the
			<filename>doc/source/</filename> folder.
			However, provided you are in the correct working copy, if you
			pick the wrong folder level, TortoiseGit will notice and suggest the
			correct level.
		</para>
		<para>
			In order to apply a patch file to your working copy, you need
			to have at least read access to the repository.
			The reason for this is that the merge program must
			reference the changes back to the revision against
			which they were made by the remote developer.
		</para>
		<para>
			From the context menu for that folder, click on
			<menuchoice>
				<guimenu>TortoiseGit</guimenu>
				<guimenuitem>Apply Patch...</guimenuitem>
			</menuchoice>
			This will bring up a file open dialog allowing you to select the
			patch file to apply. By default only <filename>.patch</filename>
			or <filename>.diff</filename>
			files are shown, but you can opt for <quote>All files</quote>.
			If you previously saved a patch to the clipboard, you can use
			<guibutton>Open from clipboard...</guibutton> in the file
			open dialog.
		</para>
		<para>
			Alternatively, if the patch file has a <filename>.patch</filename>
			or <filename>.diff</filename> extension, you can right click on it
			directly and select
			<menuchoice>
				<guimenu>TortoiseGit</guimenu>
				<guimenuitem>Apply Patch...</guimenuitem>
			</menuchoice>.
			In this case you will be prompted to enter a working copy location.
		</para>
		<para>
			These two methods just offer different ways of doing the same thing.
			With the first method you select the WC and browse to the patch file.
			With the second you select the patch file and browse to the WC.
		</para>
		<para>
			Once you have selected the patch file and working copy location,
			TortoiseMerge runs to merge the changes from the patch file
			with your working copy. A small window lists the files which have
			been changed. Double click on each one in turn, review the changes
			and save the merged files.
		</para>
		<para>
			The remote developer's patch has now been applied to your working copy,
			so you need to commit to allow everyone else to access the changes
			from the repository.
		</para>
	</sect2>
</sect1>
