[PATCH] git-format-patch-script and mailinfo updates.

[PATCH] git-format-patch-script and mailinfo updates.

 - avoid duplicating [PATCH] in the commit message body if the
   original commit has it already (happens for commits done from
   mails via applymbox).

 - check if the commit author is different from the one who is
   running the script, and emit an appropriate "From:" and
   "Date: " lines to the output.

 - with '--date', emit "Date: " line to preserve the original
   author date even for the user's own commit.

 - teach mailinfo to grok not just "From: " but "Date: ".

The patch e-mail output by format-patch starts with the first
line from the original commit message, prefixed with [PATCH],
and optionally a From: line if you are reformatting a patch
obtained from somebody else, a Date: line from the original
commit if (1) --date is specified or (2) for somebody else's
patch, and the rest of the commit message body.

Expected use of this is to move the title line from the commit
to Subject: when sending it via an e-mail, and leave the From:
and the Date: lines as the first lines of your message.

The mailinfo command has been changed to read Date: (in addition
to From: it already understands) and do sensible things when
running applymbox.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>