When describe is run with 'dirty' flag, we refresh the index
to make sure it is in sync with the filesystem before
determining if the working tree is dirty.  However, this is
not done for the codepath where the 'broken' flag is used.

This causes `git describe --broken --dirty` to false
positively report the worktree being dirty.  Refreshing the
index before running diff-index fixes the problem.

Signed-off-by: Abhijeet Sonar <redacted>
Reported-by: Paul Millar <redacted>
Suggested-by: Junio C Hamano <redacted>
---
 builtin/describe.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/builtin/describe.c b/builtin/describe.c
index e5287eddf2..2b443c155e 100644
--- a/builtin/describe.c
+++ b/builtin/describe.c

@@ -645,6 +645,20 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
 	if (argc == 0) {
 		if (broken) {
 			struct child_process cp = CHILD_PROCESS_INIT;
+			struct lock_file index_lock = LOCK_INIT;
+			int fd;
+
+			setup_work_tree();
+			prepare_repo_settings(the_repository);
+			repo_read_index(the_repository);
+			refresh_index(the_repository->index, REFRESH_QUIET|REFRESH_UNMERGED,
+				      NULL, NULL, NULL);
+			fd = repo_hold_locked_index(the_repository,
+						    &index_lock, 0);
+			if (0 <= fd)
+				repo_update_index_if_able(the_repository, &index_lock);
+
+