[PATCH] Pickaxe fixes.

A bug in the command line argument parsing code was making
pickaxe not to work at all in diff-cache and diff-files commands.
Embarrassingly enough, the working pickaxe in diff-tree tells me
that it was not working in these two commands from day one.
This patch fixes it.

Also updates the documentation to describe the --pickaxe-all option.

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

diff-cache.c

@@ -206,7 +206,7 @@ int main(int argc, const char **argv)
 			diff_setup_opt |= DIFF_SETUP_REVERSE;
 			continue;
 		}
-		if (!strcmp(arg, "-S")) {
+		if (!strncmp(arg, "-S", 2)) {
 			pickaxe = arg + 2;
 			continue;
 		}