Merge branch 'jk/diff-cc-oidfind-fix'

"log -c --find-object=X" did not work well to find a merge that
involves a change to an object X from only one parent.

* jk/diff-cc-oidfind-fix:
  combine-diff: handle --find-object in multitree code path

combine-diff.c

@@ -1450,6 +1450,42 @@ static struct combine_diff_path *find_paths_multitree(
 	return paths_head.next;
 }
 
+static int match_objfind(struct combine_diff_path *path,
+			 int num_parent,
+			 const struct oidset *set)
+{
+	int i;
+	if (oidset_contains(set, &path->oid))
+		return 1;
+	for (i = 0; i < num_parent; i++) {
+		if (oidset_contains(set, &path->parent[i].oid))
+			return 1;
+	}
+	return 0;
+}
+
+static struct combine_diff_path *combined_objfind(struct diff_options *opt,
+						  struct combine_diff_path *paths,
+						  int num_parent)
+{
+	struct combine_diff_path *ret = NULL, **tail = &ret;
+	struct combine_diff_path *p = paths;
+
+	while (p) {
+		struct combine_diff_path *next = p->next;
+
+		if (match_objfind(p, num_parent, opt->objfind)) {
+			p->next = NULL;
+			*tail = p;
+			tail = &p->next;
+		} else {
+			free(p);
+		}
+		p = next;
+	}
+
+	return ret;
+}
 
 void diff_tree_combined(const struct object_id *oid,
 			const struct oid_array *parents,
@@ -1504,10 +1540,10 @@ void diff_tree_combined(const struct object_id *oid,
 			opt->flags.follow_renames	||
 			opt->break_opt != -1	||
 			opt->detect_rename	||
-			(opt->pickaxe_opts & DIFF_PICKAXE_KINDS_MASK)	||
+			(opt->pickaxe_opts &
+			 (DIFF_PICKAXE_KINDS_MASK & ~DIFF_PICKAXE_KIND_OBJFIND)) ||
 			opt->filter;
 
-
 	if (need_generic_pathscan) {
 		/*
 		 * NOTE generic case also handles --stat, as it computes
@@ -1521,6 +1557,9 @@ void diff_tree_combined(const struct object_id *oid,
 		int stat_opt;
 		paths = find_paths_multitree(oid, parents, &diffopts);
 
+		if (opt->pickaxe_opts & DIFF_PICKAXE_KIND_OBJFIND)
+			paths = combined_objfind(opt, paths, num_parent);
+
 		/*
 		 * show stat against the first parent even
 		 * when doing combined diff.

t/t4064-diff-oidfind.sh

@@ -65,4 +65,59 @@ test_expect_success 'find a submodule' '
 	test_cmp expect actual
 '
 
+test_expect_success 'set up merge tests' '
+	test_commit base &&
+
+	git checkout -b boring base^ &&
+	echo boring >file &&
+	git add file &&
+	git commit -m boring &&
+
+	git checkout -b interesting base^ &&
+	echo interesting >file &&
+	git add file &&
+	git commit -m interesting &&
+
+	blob=$(git rev-parse interesting:file)
+'
+
+test_expect_success 'detect merge which introduces blob' '
+	git checkout -B merge base &&
+	git merge --no-commit boring &&
+	echo interesting >file &&
+	git commit -am "introduce blob" &&
+	git diff-tree --format=%s --find-object=$blob -c --name-status HEAD >actual &&
+	cat >expect <<-\EOF &&
+	introduce blob
+
+	AM	file
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'detect merge which removes blob' '
+	git checkout -B merge interesting &&
+	git merge --no-commit base &&
+	echo boring >file &&
+	git commit -am "remove blob" &&
+	git diff-tree --format=%s --find-object=$blob -c --name-status HEAD >actual &&
+	cat >expect <<-\EOF &&
+	remove blob
+
+	MA	file
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'do not detect merge that does not touch blob' '
+	git checkout -B merge interesting &&
+	git merge -m "untouched blob" base &&
+	git diff-tree --format=%s --find-object=$blob -c --name-status HEAD >actual &&
+	cat >expect <<-\EOF &&
+	untouched blob
+
+	EOF
+	test_cmp expect actual
+'
+
 test_done