[PATCH v6] describe: refresh the index when 'broken' flag is used

[Abhijeet Sonar <abhijeet.nkt@gmail.com>]

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 if a file has
different stat info than what is recorded in the index.
Running `git update-index -q --refresh` to refresh the index
before running diff-index fixes the problem.

Also add tests to deliberately update stat info of a
file before running describe to verify it behaves correctly.

Reported-by: Paul Millar <paul.millar@desy.de>
Suggested-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Phillip Wood <phillip.wood123@gmail.com>
Helped-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Abhijeet Sonar <abhijeet.nkt@gmail.com>
---
 builtin/describe.c  | 11 +++++++++++
 t/t6120-describe.sh | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/builtin/describe.c b/builtin/describe.c
index e5287eddf2..7cb9d50b36 100644
--- a/builtin/describe.c
+++ b/builtin/describe.c
@@ -53,6 +53,10 @@ static const char *diff_index_args[] = {
 	"diff-index", "--quiet", "HEAD", "--", NULL
 };
 
+static const char *update_index_args[] = {
+	"update-index", "--unmerged", "-q", "--refresh", NULL
+};
+
 struct commit_name {
 	struct hashmap_entry entry;
 	struct object_id peeled;
@@ -645,6 +649,13 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
 	if (argc == 0) {
 		if (broken) {
 			struct child_process cp = CHILD_PROCESS_INIT;
+			strvec_pushv(&cp.args, update_index_args);
+			cp.git_cmd = 1;
+			cp.no_stdin = 1;
+			cp.no_stdout = 1;
+			if (run_command(&cp))
+				child_process_clear(&cp);
+
 			strvec_pushv(&cp.args, diff_index_args);
 			cp.git_cmd = 1;
 			cp.no_stdin = 1;
diff --git a/t/t6120-describe.sh b/t/t6120-describe.sh
index e78315d23d..f8591a5b2a 100755
--- a/t/t6120-describe.sh
+++ b/t/t6120-describe.sh
@@ -671,4 +671,40 @@ test_expect_success 'setup misleading taggerdates' '
 
 check_describe newer-tag-older-commit~1 --contains unique-file~2
 
+test_expect_success 'describe --dirty with a file with changed stat' '
+	git init stat-dirty &&
+	(
+		cd stat-dirty &&
+
+		echo A >file &&
+		git add file &&
+		git commit -m A &&
+		git tag A -a -m A &&
+
+		cat file >file.new &&
+		mv file.new file &&
+		git describe --dirty >actual &&
+		echo "A" >expected &&
+		test_cmp expected actual
+	)
+'
+
+test_expect_success 'describe --dirty --broken with a file with changed stat' '
+	git init stat-dirty-broken &&
+	(
+		cd stat-dirty-broken &&
+
+		echo A >file &&
+		git add file &&
+		git commit -m A &&
+		git tag A -a -m A &&
+
+		cat file >file.new &&
+		mv file.new file &&
+		git describe --dirty --broken >actual &&
+		echo "A" >expected &&
+		test_cmp expected actual
+	)
+'
+
 test_done

Range-diff against v5:
1:  52f590b70f ! 1:  c8010b1533 describe: refresh the index when 'broken' flag is used
    @@ Commit message
         Suggested-by: Junio C Hamano <gitster@pobox.com>
         Helped-by: Junio C Hamano <gitster@pobox.com>
         Helped-by: Phillip Wood <phillip.wood123@gmail.com>
    +    Helped-by: Karthik Nayak <karthik.188@gmail.com>
         Signed-off-by: Abhijeet Sonar <abhijeet.nkt@gmail.com>
     
      ## builtin/describe.c ##
    @@ t/t6120-describe.sh: test_expect_success 'setup misleading taggerdates' '
     +		mv file.new file &&
     +		git describe --dirty >actual &&
     +		echo "A" >expected &&
    -+		test_cmp expected actual &&
    ++		test_cmp expected actual
    ++	)
    ++'
    ++
    ++test_expect_success 'describe --dirty --broken with a file with changed stat' '
    ++	git init stat-dirty-broken &&
    ++	(
    ++		cd stat-dirty-broken &&
    ++
    ++		echo A >file &&
    ++		git add file &&
    ++		git commit -m A &&
    ++		git tag A -a -m A &&
     +
     +		cat file >file.new &&
     +		mv file.new file &&
-- 
2.45.2.606.g9005149a4a.dirty