diff: factor out src/dst prefix setup

We directly manipulate diffopt's a_prefix and b_prefix to set up either
the default "a/foo" prefix or the "--no-prefix" variant. Although this
is only a few lines, it's worth pulling these into their own functions.
That lets us avoid one repetition already in this patch, but will also
give us a cleaner interface for callers which want to tweak this
setting.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/diff.h b/diff.h
index 8d770b1d57..2af10bc585 100644
--- a/diff.h
+++ b/diff.h
@@ -497,6 +497,8 @@ void diff_tree_combined(const struct object_id *oid, const struct oid_array *par
 void diff_tree_combined_merge(const struct commit *commit, struct rev_info *rev);
 
 void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const char *b);
+void diff_set_noprefix(struct diff_options *options);
+void diff_set_default_prefix(struct diff_options *options);
 
 int diff_can_quit_early(struct diff_options *);