[PATCH] diff.c: clean temporary files

[PATCH] diff.c: clean temporary files

When diff-cache -p and friends are interrupted, they can leave
their temporary files behind.  Also when the external diff
program is killed instead of exiting (this usually happens when
piping the output to a pager, which can cause SIGPIPE when the
user quits viewing the diff early), they incorrectly died
without cleaning their temporary file.

This fixes these problems.

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