[PATCH 1/2] branch: description for orphan branch errors

["Rubén Justo" <rjusto@gmail.com>]

In bcfc82bd48 (branch: description for non-existent branch errors,
2022-10-08) we used "strcmp(head, branch)" to check if we're asked to
operate in a branch that is the current HEAD, and
"ref_exists(branch_ref)" to check if it points to a valid ref, i.e. it
is an orphan branch.  We are doing this with the intention of avoiding
the confusing error: "No branch named..."

If we're asked to operate with an orphan branch, but it is on a
different worktree, "strcmp(head, branch)" is not going to match:

	$ git worktree add orphan-worktree --detach
	$ git -C orphan-worktree checkout --orphan orpha-branch
	$ git branch -m orpha-branch orphan-branch
	fatal: No branch named 'orpha-branch'.

Let's do the check for HEAD in any worktree in the repository, removing
the "strcmp" and using the helper introduced in 31ad6b61bd (branch: add
branch_checked_out() helper, 2022-06-15)

This commit also extends the tests introduced on bcfc82bd48, in
t3202-show-branch, to cover not just the initial branch but any orphan
branch.

Signed-off-by: Rubén Justo <rjusto@gmail.com>
---
 builtin/branch.c       |  8 ++++----
 t/t3202-show-branch.sh | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index f63fd45edb..954008e51d 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -528,8 +528,8 @@ static void copy_or_rename_branch(const char *oldname, const char *newname, int
 			die(_("Invalid branch name: '%s'"), oldname);
 	}
 
-	if ((copy || strcmp(head, oldname)) && !ref_exists(oldref.buf)) {
-		if (copy && !strcmp(head, oldname))
+	if ((copy || !branch_checked_out(oldref.buf)) && !ref_exists(oldref.buf)) {
+		if (copy && branch_checked_out(oldref.buf))
 			die(_("No commit on branch '%s' yet."), oldname);
 		else
 			die(_("No branch named '%s'."), oldname);
@@ -806,7 +806,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 
 		strbuf_addf(&branch_ref, "refs/heads/%s", branch_name);
 		if (!ref_exists(branch_ref.buf))
-			error((!argc || !strcmp(head, branch_name))
+			error((!argc || branch_checked_out(branch_ref.buf))
 			      ? _("No commit on branch '%s' yet.")
 			      : _("No branch named '%s'."),
 			      branch_name);
@@ -851,7 +851,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		}
 
 		if (!ref_exists(branch->refname)) {
-			if (!argc || !strcmp(head, branch->name))
+			if (!argc || branch_checked_out(branch->refname))
 				die(_("No commit on branch '%s' yet."), branch->name);
 			die(_("branch '%s' does not exist"), branch->name);
 		}
diff --git a/t/t3202-show-branch.sh b/t/t3202-show-branch.sh
index ea7cfd1951..acaedac34e 100755
--- a/t/t3202-show-branch.sh
+++ b/t/t3202-show-branch.sh
@@ -221,4 +221,40 @@ test_expect_success 'fatal descriptions on non-existent branch' '
 	test_cmp expect actual
 '
 
+test_expect_success 'error descriptions on orphan or unborn-yet branch' '
+	cat >expect <<-EOF &&
+	error: No commit on branch '\''orphan-branch'\'' yet.
+	EOF
+	test_when_finished git worktree remove -f orphan-worktree &&
+	git worktree add orphan-worktree --detach &&
+	git -C orphan-worktree checkout --orphan orphan-branch &&
+	test_must_fail git -C orphan-worktree branch --edit-description 2>actual && # implicit branch
+	test_cmp expect actual &&
+	test_must_fail git -C orphan-worktree branch --edit-description orphan-branch 2>actual && # explicit branch
+	test_cmp expect actual &&
+	test_must_fail git branch --edit-description orphan-branch 2>actual && # different worktree
+	test_cmp expect actual
+'
+
+test_expect_success 'fatal descriptions on orphan or unborn-yet branch' '
+	cat >expect <<-EOF &&
+	fatal: No commit on branch '\''orphan-branch'\'' yet.
+	EOF
+	test_when_finished git worktree remove -f orphan-worktree &&
+	git worktree add orphan-worktree --detach &&
+	git -C orphan-worktree checkout --orphan orphan-branch &&
+	test_must_fail git -C orphan-worktree branch --set-upstream-to=non-existent 2>actual && # implicit branch
+	test_cmp expect actual &&
+	test_must_fail git -C orphan-worktree branch --set-upstream-to=non-existent orphan-branch 2>actual && # explicit branch
+	test_cmp expect actual &&
+	test_must_fail git branch --set-upstream-to=non-existent orphan-branch 2>actual && # different worktree
+	test_cmp expect actual &&
+	test_must_fail git -C orphan-worktree branch -c new-branch 2>actual && # implicit branch
+	test_cmp expect actual &&
+	test_must_fail git -C orphan-worktree branch -c orphan-branch new-branch 2>actual && # explicit branch
+	test_cmp expect actual &&
+	test_must_fail git branch -c orphan-branch new-branch 2>actual && # different worktree
+	test_cmp expect actual
+'
+
 test_done
-- 
2.39.0