merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/contrib/svn-fe/svn-fe.txt

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+svn-fe(1)
+=========
+
+NAME
+----
+svn-fe - convert an SVN "dumpfile" to a fast-import stream
+
+SYNOPSIS
+--------
+[verse]
+mkfifo backchannel &&
+svnadmin dump --deltas REPO |
+	svn-fe [url] 3<backchannel |
+	git fast-import --cat-blob-fd=3 3>backchannel
+
+DESCRIPTION
+-----------
+
+Converts a Subversion dumpfile into input suitable for
+git-fast-import(1) and similar importers. REPO is a path to a
+Subversion repository mirrored on the local disk. Remote Subversion
+repositories can be mirrored on local disk using the `svnsync`
+command.
+
+Note: this tool is very young.  The details of its commandline
+interface may change in backward incompatible ways.
+
+INPUT FORMAT
+------------
+Subversion's repository dump format is documented in full in
+`notes/dump-load-format.txt` from the Subversion source tree.
+Files in this format can be generated using the 'svnadmin dump' or
+'svk admin dump' command.
+
+OUTPUT FORMAT
+-------------
+The fast-import format is documented by the git-fast-import(1)
+manual page.
+
+NOTES
+-----
+Subversion dumps do not record a separate author and committer for
+each revision, nor do they record a separate display name and email
+address for each author.  Like git-svn(1), 'svn-fe' will use the name
+
+---------
+user <user@UUID>
+---------
+
+as committer, where 'user' is the value of the `svn:author` property
+and 'UUID' the repository's identifier.
+
+To support incremental imports, 'svn-fe' puts a `git-svn-id` line at
+the end of each commit log message if passed a URL on the command
+line.  This line has the form `git-svn-id: URL@REVNO UUID`.
+
+The resulting repository will generally require further processing
+to put each project in its own repository and to separate the history
+of each branch.  The 'git filter-branch --subdirectory-filter' command
+may be useful for this purpose.
+
+BUGS
+----
+Empty directories and unknown properties are silently discarded.
+
+The exit status does not reflect whether an error was detected.
+
+SEE ALSO
+--------
+git-svn(1), svn2git(1), svk(1), git-filter-branch(1), git-fast-import(1),
+https://svn.apache.org/repos/asf/subversion/trunk/notes/dump-load-format.txt