Teach git diff-tree --stdin to diff trees

When feeding trees on the command line, you can give exactly two
trees, not three nor one; --stdin now supports this "two tree" form on
its input, in addition to accepting lines with one or more commits.

When diffing trees (either specified on the command line or from the
standard input), the -s, -v, --pretty, --abbrev-commit, --encoding,
--no-commit-id, and --always options are ignored, since they do not
apply to trees; and the -m, -c, and --cc options are ignored since
they would be meaningful only with three or more trees, which is not
supported (yet).

Signed-off-by: Karl Hasselström <kha@treskal.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 29 insertions, 4 deletions

diff --git a/builtin-diff-tree.c b/builtin-diff-tree.c
index ebbd6317c..1138c2da7 100644
--- a/builtin-diff-tree.c
+++ b/builtin-diff-tree.c
@@ -42,21 +42,46 @@ static int stdin_diff_commit(struct commit *commit, char *line, int len)
 	return log_tree_commit(&log_tree_opt, commit);
 }
 
+/* Diff two trees. */
+static int stdin_diff_trees(struct tree *tree1, char *line, int len)
+{
+	unsigned char sha1[20];
+	struct tree *tree2;
+	if (len != 82 || !isspace(line[40]) || get_sha1_hex(line + 41, sha1))
+		return error("Need exactly two trees, separated by a space");
+	tree2 = lookup_tree(sha1);
+	if (!tree2 || parse_tree(tree2))
+		return -1;
+	printf("%s %s\n", sha1_to_hex(tree1->object.sha1),
+			  sha1_to_hex(tree2->object.sha1));
+	diff_tree_sha1(tree1->object.sha1, tree2->object.sha1,
+		       "", &log_tree_opt.diffopt);
+	log_tree_diff_flush(&log_tree_opt);
+	return 0;
+}
+
 static int diff_tree_stdin(char *line)
 {
 	int len = strlen(line);
 	unsigned char sha1[20];
-	struct commit *commit;
+	struct object *obj;
 
 	if (!len || line[len-1] != '\n')
 		return -1;
 	line[len-1] = 0;
 	if (get_sha1_hex(line, sha1))
 		return -1;
-	commit = lookup_commit(sha1);
-	if (!commit || parse_commit(commit))
+	obj = lookup_object(sha1);
+	obj = obj ? obj : parse_object(sha1);
+	if (!obj)
 		return -1;
-	return stdin_diff_commit(commit, line, len);
+	if (obj->type == OBJ_COMMIT)
+		return stdin_diff_commit((struct commit *)obj, line, len);
+	if (obj->type == OBJ_TREE)
+		return stdin_diff_trees((struct tree *)obj, line, len);
+	error("Object %s is a %s, not a commit or tree",
+	      sha1_to_hex(sha1), typename(obj->type));
+	return -1;
 }
 
 static const char diff_tree_usage[] =