1 files changed, 27 insertions, 8 deletions
diff --git a/diff-lib.c b/diff-lib.c
index 50521e2093..346fdcf0b0 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -405,14 +405,8 @@ static void do_oneway_diff(struct unpack_trees_options *o,
 	/* if the entry is not checked out, don't examine work tree */
 	cached = o->index_only ||
 		(idx && ((idx->ce_flags & CE_VALID) || ce_skip_worktree(idx)));
-	/*
-	 * Backward compatibility wart - "diff-index -m" does
-	 * not mean "do not ignore merges", but "match_missing".
-	 *
-	 * But with the revision flag parsing, that's found in
-	 * "!revs->ignore_merges".
-	 */
-	match_missing = !revs->ignore_merges;
+
+	match_missing = revs->match_missing;
 
 	if (cached && idx && ce_stage(idx)) {
 		struct diff_filepair *pair;
@@ -571,3 +565,28 @@ int index_differs_from(struct repository *r,
 	object_array_clear(&rev.pending);
 	return (rev.diffopt.flags.has_changes != 0);
 }
+
+static struct strbuf *idiff_prefix_cb(struct diff_options *opt, void *data)
+{
+	return data;
+}
+
+void show_interdiff(const struct object_id *oid1, const struct object_id *oid2,
+		    int indent, struct diff_options *diffopt)
+{
+	struct diff_options opts;
+	struct strbuf prefix = STRBUF_INIT;
+
+	memcpy(&opts, diffopt, sizeof(opts));
+	opts.output_format = DIFF_FORMAT_PATCH;
+	opts.output_prefix = idiff_prefix_cb;
+	strbuf_addchars(&prefix, ' ', indent);
+	opts.output_prefix_data = &prefix;
+	diff_setup_done(&opts);
+
+	diff_tree_oid(oid1, oid2, "", &opts);
+	diffcore_std(&opts);
+	diff_flush(&opts);
+
+	strbuf_release(&prefix);
+}