[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 --git a/diff-files.c b/diff-files.c
index bd0eb95..8ab7915 100644
--- a/diff-files.c
+++ b/diff-files.c
@@ -53,7 +53,7 @@
 			diff_output_format = DIFF_FORMAT_MACHINE;
 		else if (!strcmp(argv[1], "-R"))
 			diff_setup_opt |= DIFF_SETUP_REVERSE;
-		else if (!strcmp(argv[1], "-S"))
+		else if (!strncmp(argv[1], "-S", 2))
 			pickaxe = argv[1] + 2;
 		else if (!strcmp(argv[1], "--pickaxe-all"))
 			pickaxe_opts = DIFF_PICKAXE_ALL;