diff: make more cases implicit --no-index

When specifying an absolute path, or a relative path pointing outside
the working tree, do not fail, but roll your own diffopt parsing,
and execute a --no-index diff.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/diff.h b/diff.h
index 4043cec04e..4b435e8b19 100644
--- a/diff.h
+++ b/diff.h
@@ -222,6 +222,8 @@ 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 setup_diff_no_index(struct rev_info *revs,
+		int argc, const char ** argv, int nongit, const char *prefix);
 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);