[PATCH] Add merge detection to git-cvsimport

[PATCH] Add merge detection to git-cvsimport

Added -m and -M flags for git-cvsimport to detect merge commits in cvs.
While this trusts the commit message, in repositories where merge commits
indicate 'merged from FOOBRANCH' the import works surprisingly well.

Even if some merges from CVS are bogus or incomplete, the resulting
branches are in better state to go forward (and merge) than without any
merge detection.

Signed-off-by: Martin Langhoff <martin.langhoff@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>