status: fix branch shown when not only bisecting

In 83c750acde (wt-status.*: better advice for git status added,
2012-06-05), git-status received new informative messages to describe
the ongoing work in a worktree.

These messages were enhanced in 0722c805d6 (status: show the branch name
if possible in in-progress info, 2013-02-03), to show, if possible, the
branch where the operation was initiated.

Since then, we show incorrect information when several operations are in
progress and one of them is bisect:

   $ git checkout -b foo
   $ GIT_SEQUENCE_EDITOR='echo break >' git rebase -i HEAD~
   $ git checkout -b bar
   $ git bisect start
   $ git status
   ...

   You are currently editing a commit while rebasing branch 'bar' on '...'.

   You are currently bisecting, started from branch 'bar'.

   ...

Note that we erroneously say "while rebasing branch 'bar'" when we
should be referring to "foo".

This must have gone unnoticed for so long because it must be unusual to
start a bisection while another operation is in progress.  And even less
usual to involve different branches.

It caught my attention reviewing a leak introduced in 8b87cfd000
(wt-status: move strbuf into read_and_strip_branch(), 2013-03-16).

A simple change to deal with this situation can be to record in struct
wt_status_state, the branch where the bisect starts separately from the
branch related to other operations.

Let's do it and so we'll be able to display correct information and
we'll avoid the leak as well.

Signed-off-by: Rubén Justo <rjusto@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

branch.c

@@ -419,9 +419,9 @@ static void prepare_checked_out_branches(void)
 		wt_status_state_free_buffers(&state);
 
 		if (wt_status_check_bisect(wt, &state) &&
-		    state.branch) {
+		    state.bisecting_from) {
 			struct strbuf ref = STRBUF_INIT;
-			strbuf_addf(&ref, "refs/heads/%s", state.branch);
+			strbuf_addf(&ref, "refs/heads/%s", state.bisecting_from);
 			old = strmap_put(&current_checked_out_branches,
 					 ref.buf,
 					 xstrdup(wt->path));

ref-filter.c

@@ -1773,7 +1773,7 @@ char *get_head_description(void)
 				    state.detached_from);
 	} else if (state.bisect_in_progress)
 		strbuf_addf(&desc, _("(no branch, bisect started on %s)"),
-			    state.branch);
+			    state.bisecting_from);
 	else if (state.detached_from) {
 		if (state.detached_at)
 			strbuf_addf(&desc, _("(HEAD detached at %s)"),

t/t7512-status-help.sh

@@ -692,6 +692,34 @@ EOF
 '
 
 
+test_expect_success 'status when bisecting while rebasing' '
+	git reset --hard main &&
+	test_when_finished "git rebase --abort" &&
+	ONTO=$(git rev-parse --short HEAD^) &&
+	FAKE_LINES="break" git rebase -i HEAD^ &&
+	test_when_finished "git checkout -" &&
+	git checkout -b bisect_while_rebasing &&
+	test_when_finished "git bisect reset" &&
+	git bisect start &&
+	cat >expected <<EOF &&
+On branch bisect_while_rebasing
+Last command done (1 command done):
+   break
+No commands remaining.
+You are currently editing a commit while rebasing branch '\''bisect'\'' on '\''$ONTO'\''.
+  (use "git commit --amend" to amend the current commit)
+  (use "git rebase --continue" once you are satisfied with your changes)
+
+You are currently bisecting, started from branch '\''bisect_while_rebasing'\''.
+  (use "git bisect reset" to get back to the original branch)
+
+nothing to commit (use -u to show untracked files)
+EOF
+	git status --untracked-files=no >actual &&
+	test_cmp expected actual
+'
+
+
 test_expect_success 'status when rebase --apply conflicts with statushints disabled' '
 	git reset --hard main &&
 	git checkout -b statushints_disabled &&

worktree.c

@@ -396,9 +396,9 @@ int is_worktree_being_bisected(const struct worktree *wt,
 
 	memset(&state, 0, sizeof(state));
 	found_bisect = wt_status_check_bisect(wt, &state) &&
-		       state.branch &&
+		       state.bisecting_from &&
 		       skip_prefix(target, "refs/heads/", &target) &&
-		       !strcmp(state.branch, target);
+		       !strcmp(state.bisecting_from, target);
 	wt_status_state_free_buffers(&state);
 	return found_bisect;
 }

wt-status.c

@@ -858,6 +858,7 @@ void wt_status_state_free_buffers(struct wt_status_state *state)
 	FREE_AND_NULL(state->branch);
 	FREE_AND_NULL(state->onto);
 	FREE_AND_NULL(state->detached_from);
+	FREE_AND_NULL(state->bisecting_from);
 }
 
 static void wt_longstatus_print_unmerged(struct wt_status *s)
@@ -1565,10 +1566,10 @@ static void show_revert_in_progress(struct wt_status *s,
 static void show_bisect_in_progress(struct wt_status *s,
 				    const char *color)
 {
-	if (s->state.branch)
+	if (s->state.bisecting_from)
 		status_printf_ln(s, color,
 				 _("You are currently bisecting, started from branch '%s'."),
-				 s->state.branch);
+				 s->state.bisecting_from);
 	else
 		status_printf_ln(s, color,
 				 _("You are currently bisecting."));
@@ -1729,7 +1730,7 @@ int wt_status_check_bisect(const struct worktree *wt,
 
 	if (!stat(worktree_git_path(wt, "BISECT_LOG"), &st)) {
 		state->bisect_in_progress = 1;
-		state->branch = get_branch(wt, "BISECT_START");
+		state->bisecting_from = get_branch(wt, "BISECT_START");
 		return 1;
 	}
 	return 0;

wt-status.h

@@ -94,6 +94,7 @@ struct wt_status_state {
 	char *branch;
 	char *onto;
 	char *detached_from;
+	char *bisecting_from;
 	struct object_id detached_oid;
 	struct object_id revert_head_oid;
 	struct object_id cherry_pick_head_oid;