diff: add diff_line_prefix function

This is a helper function to call the diff output_prefix function and
return its value as a C string, allowing us to greatly simplify
everywhere that needs to get the output prefix.

Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/diff.h b/diff.h
index a47bae4..76830e2 100644
--- a/diff.h
+++ b/diff.h
@@ -174,6 +174,9 @@ const char *diff_get_color(int diff_use_color, enum color_diff ix);
 	diff_get_color((o)->use_color, ix)
 
 
+const char *diff_line_prefix(struct diff_options *);
+
+
 extern const char mime_boundary_leader[];
 
 extern void diff_tree_setup_paths(const char **paths, struct diff_options *);