git-svn: Fix for rewriteRoot URL containing username.

git-svn: Fix for rewriteRoot URL containing username.

If the new svn root URL given with the svn-remote.<repo>.rewriteRoot config option
(or by the --rewrite-root option to 'git svn init') contains a username
(such as 'svn+ssh://username@example.com/repo'), find_by_url() cannot find
the repository URL, because the URL contained in the commit message does have
the username removed.

Signed-off-by: Dévai Tamás <devait@mailbox.sk>
Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>