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Merge branch 'sl/git-svn-docs'

* sl/git-svn-docs:
git-svn: Note about tags.
git-svn: Expand documentation for --follow-parent
git-svn: Recommend use of structure options.
git-svn: Document branches with at-sign(@).

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Documentation/git-svn.txt

 	Default: "svn"
 
 --follow-parent::
+	This option is only relevant if we are tracking branches (using
+	one of the repository layout options --trunk, --tags,
+	--branches, --stdlayout). For each tracked branch, try to find
+	out where its revision was copied from, and set
+	a suitable parent in the first git commit for the branch.
 	This is especially helpful when we're tracking a directory
-	that has been moved around within the repository, or if we
-	started tracking a branch and never tracked the trunk it was
-	descended from. This feature is enabled by default, use
+	that has been moved around within the repository.  If this
+	feature is disabled, the branches created by 'git svn' will all
+	be linear and not share any history, meaning that there will be
+	no information on where branches were branched off or merged.
+	However, following long/convoluted histories can take a long
+	time, so disabling this feature may speed up the cloning
+	process. This feature is enabled by default, use
 	--no-follow-parent to disable it.
 +
 [verse]
 BASIC EXAMPLES
 --------------
 
-Tracking and contributing to the trunk of a Subversion-managed project:
+Tracking and contributing to the trunk of a Subversion-managed project
+(ignoring tags and branches):
 
 ------------------------------------------------------------------------
 # Clone a repo (like git clone):
 (complete with a trunk, tags and branches):
 
 ------------------------------------------------------------------------
-# Clone a repo (like git clone):
-	git svn clone http://svn.example.com/project -T trunk -b branches -t tags
+# Clone a repo with standard SVN directory layout (like git clone):
+	git svn clone http://svn.example.com/project --stdlayout
+# Or, if the repo uses a non-standard directory layout:
+	git svn clone http://svn.example.com/project -T tr -b branch -t tag
 # View all branches and tags you have cloned:
 	git branch -r
 # Create a new branch in SVN
 users keep history as linear as possible inside git to ease
 compatibility with SVN (see the CAVEATS section below).
 
+HANDLING OF SVN BRANCHES
+------------------------
+If 'git svn' is configured to fetch branches (and --follow-branches
+is in effect), it sometimes creates multiple git branches for one
+SVN branch, where the addtional branches have names of the form
+'branchname@nnn' (with nnn an SVN revision number).  These additional
+branches are created if 'git svn' cannot find a parent commit for the
+first commit in an SVN branch, to connect the branch to the history of
+the other branches.
+
+Normally, the first commit in an SVN branch consists
+of a copy operation. 'git svn' will read this commit to get the SVN
+revision the branch was created from. It will then try to find the
+git commit that corresponds to this SVN revision, and use that as the
+parent of the branch. However, it is possible that there is no suitable
+git commit to serve as parent.  This will happen, among other reasons,
+if the SVN branch is a copy of a revision that was not fetched by 'git
+svn' (e.g. because it is an old revision that was skipped with
+'--revision'), or if in SVN a directory was copied that is not tracked
+by 'git svn' (such as a branch that is not tracked at all, or a
+subdirectory of a tracked branch). In these cases, 'git svn' will still
+create a git branch, but instead of using an existing git commit as the
+parent of the branch, it will read the SVN history of the directory the
+branch was copied from and create appropriate git commits.  This is
+indicated by the message "Initializing parent: <branchname>".
+
+Additionally, it will create a special branch named
+'<branchname>@<SVN-Revision>', where <SVN-Revision> is the SVN revision
+number the branch was copied from.  This branch will point to the newly
+created parent commit of the branch.  If in SVN the branch was deleted
+and later recreated from a different version, there will be multiple
+such branches with an '@'.
+
+Note that this may mean that multiple git commits are created for a
+single SVN revision.
+
+An example: in an SVN repository with a standard
+trunk/tags/branches layout, a directory trunk/sub is created in r.100.
+In r.200, trunk/sub is branched by copying it to branches/. 'git svn
+clone -s' will then create a branch 'sub'. It will also create new git
+commits for r.100 through r.199 and use these as the history of branch
+'sub'. Thus there will be two git commits for each revision from r.100
+to r.199 (one containing trunk/, one containing trunk/sub/). Finally,
+it will create a branch 'sub@200' pointing to the new parent commit of
+branch 'sub' (i.e. the commit for r.200 and trunk/sub/).
+
 CAVEATS
 -------
 
 you've already pushed to a remote repository for other users, and
 dcommit with SVN is analogous to that.
 
+When cloning an SVN repository, if none of the options for describing
+the repository layout is used (--trunk, --tags, --branches,
+--stdlayout), 'git svn clone' will create a git repository with
+completely linear history, where branches and tags appear as separate
+directories in the working copy.  While this is the easiest way to get a
+copy of a complete repository, for projects with many branches it will
+lead to a working copy many times larger than just the trunk. Thus for
+projects using the standard directory structure (trunk/branches/tags),
+it is recommended to clone with option '--stdlayout'. If the project
+uses a non-standard structure, and/or if branches and tags are not
+required, it is easiest to only clone one directory (typically trunk),
+without giving any repository layout options.  If the full history with
+branches and tags is required, the options '--trunk' / '--branches' /
+'--tags' must be used.
+
 When using multiple --branches or --tags, 'git svn' does not automatically
 handle name collisions (for example, if two branches from different paths have
 the same name, or if a branch and a tag have the same name).  In these cases,
 renamed and copied files is fully supported if they're similar enough
 for git to detect them.
 
+In SVN, it is possible (though discouraged) to commit changes to a tag
+(because a tag is just a directory copy, thus technically the same as a
+branch). When cloning an SVN repository, 'git svn' cannot know if such a
+commit to a tag will happen in the future. Thus it acts conservatively
+and imports all SVN tags as branches, prefixing the tag name with 'tags/'.
+
 CONFIGURATION
 -------------