git-apply: safety fixes

git-apply: safety fixes

This was triggered by me testing the "@@" numbering shorthand by GNU
patch, which not only showed that git-apply thought it meant the number
was duplicated (when it means that the second number is 1), but my tests
showed than when git-apply mis-understood the number, it would then not
raise an alarm about it if the patch ended early.

Now, this doesn't actually _matter_, since with a three-line context, the
only case that "x,1" will be shorthanded to "x" is when x itself is 1 (in
which case git-apply got it right), but the fact that git-apply would also
silently accept truncated patches was a missed opportunity for additional
sanity-checking.

So make git-apply refuse to look at a patch fragment that ends early.

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