vcs-svn: save marks for imported commits

This way, a person can use

	svnadmin dump $path |
	svn-fe |
	git fast-import --relative-marks --export-marks=svn-revs

to get a list of what commit corresponds to each svn revision (plus
some irrelevant blob names) in .git/info/fast-import/svn-revs.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

vcs-svn/fast_export.c

@@ -63,6 +63,7 @@ void fast_export_commit(uint32_t revision, uint32_t author, char *log,
 		*gitsvnline = '\0';
 	}
 	printf("commit refs/heads/master\n");
+	printf("mark :%"PRIu32"\n", revision);
 	printf("committer %s <%s@%s> %ld +0000\n",
 		   ~author ? pool_fetch(author) : "nobody",
 		   ~author ? pool_fetch(author) : "nobody",