Documentation: new option -P for git-svnimport

Documentation: new option -P for git-svnimport.
Signed-off-by: NQuy Tonthat <qtonthat@gmail.com>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Documentation/git-svnimport.txt

@@ -15,6 +15,7 @@ SYNOPSIS
 		[ -b branch_subdir ] [ -T trunk_subdir ] [ -t tag_subdir ]
 		[ -s start_chg ] [ -m ] [ -r ] [ -M regex ]
 		[ -I <ignorefile_name> ] [ -A <author_file> ]
+		[ -P <path_from_trunk> ]
 		<SVN_repository_URL> [ <path> ]
 
 
@@ -107,6 +108,14 @@ repository without -A.
 	Formerly, this option controlled how many revisions to pull,
 	due to SVN memory leaks. (These have been worked around.)
 
+-P <path_from_trunk>::
+	Partial import of the SVN tree.
+
+	By default, the whole tree on the SVN trunk (/trunk) is imported.
+	'-P my/proj' will import starting only from '/trunk/my/proj'.
+	This option is useful when you want to import one project from a
+	svn repo which hosts multiple projects under the same trunk.
+
 -v::
 	Verbosity: let 'svnimport' report what it is doing.