fix cherry-pick/revert status when doing multiple commits

The status report for an in-progress cherry-pick does not show the
current commit if the cherry-pick happens as part of a series of
multiple commits:

 $ git cherry-pick <commit1> <commit2>
 < one of the cherry-picks fails to merge clean >
 Cherry-pick currently in progress.
  (run "git cherry-pick --continue" to continue)
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

 $ git status
 On branch <branch>
 Your branch is ahead of '<upstream>' by 1 commit.
   (use "git push" to publish your local commits)

 Cherry-pick currently in progress.
   (run "git cherry-pick --continue" to continue)
   (use "git cherry-pick --skip" to skip this patch)
   (use "git cherry-pick --abort" to cancel the cherry-pick operation)

The show_cherry_pick_in_progress() function prints "Cherry-pick
currently in progress". That function does have a more verbose print
based on whether the cherry_pick_head_oid is null or not. If it is not
null, then a more helpful message including which commit is actually
being picked is displayed.

The introduction of the "Cherry-pick currently in progress" message
comes from 4a72486de9 ("fix cherry-pick/revert status after commit",
2019-04-17). This commit modified wt_status_get_state() in order to
detect that a cherry-pick was in progress even if the user has used `git
commit` in the middle of the sequence.

The check used to detect this is the call to sequencer_get_last_command.
If the sequencer indicates that the lass command was a REPLAY_PICK, then
the state->cherry_pick_in_progress is set to 1 and the
cherry_pick_head_oid is initialized to the null_oid. Similar behavior is
done for the case of REPLAY_REVERT.

It happens that this call of sequencer_get_last_command will always
report the action even if the user hasn't interrupted anything. Thus,
during a range of cherry-picks or reverts, the cherry_pick_head_oid and
revert_head_oid will always be overwritten and initialized to the null
oid.

This results in status always displaying the terse message which does
not include commit information.

Fix this by adding an additional check so that we do not re-initialize
the cherry_pick_head_oid or revert_head_oid if we have already set the
cherry_pick_in_progress or revert_in_progress bits. This ensures that
git status will display the more helpful information when its available.
Add a test case covering this behavior.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7512-status-help.sh

@@ -774,6 +774,28 @@ EOF
 	test_cmp expected actual
 '
 
+test_expect_success 'status when cherry-picking multiple commits' '
+	git reset --hard cherry_branch &&
+	test_when_finished "git cherry-pick --abort" &&
+	test_must_fail git cherry-pick cherry_branch_second one_cherry &&
+	TO_CHERRY_PICK=$(git rev-parse --short CHERRY_PICK_HEAD) &&
+	cat >expected <<EOF &&
+On branch cherry_branch
+You are currently cherry-picking commit $TO_CHERRY_PICK.
+  (fix conflicts and run "git cherry-pick --continue")
+  (use "git cherry-pick --skip" to skip this patch)
+  (use "git cherry-pick --abort" to cancel the cherry-pick operation)
+
+Unmerged paths:
+  (use "git add <file>..." to mark resolution)
+	both modified:   main.txt
+
+no changes added to commit (use "git add" and/or "git commit -a")
+EOF
+	git status --untracked-files=no >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'status when cherry-picking after committing conflict resolution' '
 	git reset --hard cherry_branch &&
 	test_when_finished "git cherry-pick --abort" &&

wt-status.c

@@ -1780,10 +1780,10 @@ void wt_status_get_state(struct repository *r,
 		oidcpy(&state->revert_head_oid, &oid);
 	}
 	if (!sequencer_get_last_command(r, &action)) {
-		if (action == REPLAY_PICK) {
+		if (action == REPLAY_PICK && !state->cherry_pick_in_progress) {
 			state->cherry_pick_in_progress = 1;
 			oidcpy(&state->cherry_pick_head_oid, null_oid());
-		} else {
+		} else if (action == REPLAY_REVERT && !state->revert_in_progress) {
 			state->revert_in_progress = 1;
 			oidcpy(&state->revert_head_oid, null_oid());
 		}