Teach git-diff-files the new option `--no-index`

With this flag and given two paths, git-diff-files behaves as a GNU diff
lookalike (plus the git goodies like --check, colour, etc.).  This flag
is also available in git-diff.  It also works outside of a git repository.

In addition, if git-diff{,-files} is called without revision or stage
parameter, and with exactly two paths at least one of which is not tracked,
the default is --no-index.

So, you can now say

	git diff /etc/inittab /etc/fstab

and it actually works!

This also unifies the duplicated argument parsing between cmd_diff_files()
and builtin_diff_files().

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/diff.h b/diff.h
index eece65ddcc..b608828261 100644
--- a/diff.h
+++ b/diff.h
@@ -219,6 +219,7 @@ extern void diff_flush(struct diff_options*);
 extern const char *diff_unique_abbrev(const unsigned char *, int);
 
 extern int run_diff_files(struct rev_info *revs, int silent_on_removed);
+extern int run_diff_files_cmd(struct rev_info *revs, int argc, const char **argv);
 
 extern int run_diff_index(struct rev_info *revs, int cached);