[PATCH v3 2/3] branch: description for orphan branch errors

["Rubén Justo" <rjusto@gmail.com>]

In bcfc82bd48 (branch: description for non-existent branch errors,
2022-10-08) we checked the current HEAD to detect if the branch to
operate with is an orphan branch, so as to avoid the confusing error:
"No branch named...".

If we are asked to operate with an orphan branch in a different working
tree than the current one, we need to check the HEAD in that different
working tree.

Let's extend the check we did in bcfc82db48, to all HEADs in the
repository, using the helper introduced in 31ad6b61bd (branch: add
branch_checked_out() helper, 2022-06-15)

"die_if_branch_is_being_rebased_or_bisected()" already returns whether
the branch to operate with is HEAD in any worktree in the repository.
Let's use this information in "copy_or_rename_branch()", instead of the
helper.

Note that we now call "die_if_branch_is_being_rebased_or_bisected()"
earlier, which introduces a change in the error displayed when a
combination of unsupported conditions occur simultaneously: the desired
destination name is invalid, and the branch to operate with is being
rebased or bisected.  i.e. with "foo" being rebased or bisected, this:

	$ git branch -m foo /
	fatal: '/' is not a valid branch name.

... becomes:

	$ git branch -m foo /
	fatal: Branch refs/heads/foo is being ...

Signed-off-by: Rubén Justo <rjusto@gmail.com>
---
 builtin/branch.c       | 25 +++++++++++--------------
 t/t3202-show-branch.sh | 18 ++++++++++++++++++
 2 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index 89198fa5bf..28cec344ad 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -536,12 +536,12 @@ 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))
-			die(_("No commit on branch '%s' yet."), oldname);
-		else
-			die(_("No branch named '%s'."), oldname);
-	}
+	oldref_is_head = die_if_branch_is_being_rebased_or_bisected(oldref.buf);
+
+	if ((copy || !oldref_is_head) && !ref_exists(oldref.buf))
+		die(oldref_is_head
+		    ? _("No commit on branch '%s' yet.")
+		    : _("No branch named '%s'."), oldname);
 
 	/*
 	 * A command like "git branch -M currentbranch currentbranch" cannot
@@ -552,8 +552,6 @@ static void copy_or_rename_branch(const char *oldname, const char *newname, int
 	else
 		validate_new_branchname(newname, &newref, force);
 
-	oldref_is_head = die_if_branch_is_being_rebased_or_bisected(oldref.buf);
-
 	if (!skip_prefix(oldref.buf, "refs/heads/", &interpreted_oldname) ||
 	    !skip_prefix(newref.buf, "refs/heads/", &interpreted_newname)) {
 		BUG("expected prefix missing for refs");
@@ -814,7 +812,7 @@ 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);
@@ -858,11 +856,10 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 			die(_("no such branch '%s'"), argv[0]);
 		}
 
-		if (!ref_exists(branch->refname)) {
-			if (!argc || !strcmp(head, branch->name))
-				die(_("No commit on branch '%s' yet."), branch->name);
-			die(_("branch '%s' does not exist"), branch->name);
-		}
+		if (!ref_exists(branch->refname))
+			die((!argc || branch_checked_out(branch->refname))
+			    ? _("No commit on branch '%s' yet.")
+			    : _("branch '%s' does not exist"), branch->name);
 
 		dwim_and_setup_tracking(the_repository, branch->name,
 					new_upstream, BRANCH_TRACK_OVERRIDE,
diff --git a/t/t3202-show-branch.sh b/t/t3202-show-branch.sh
index ea7cfd1951..be20ebe1d5 100755
--- a/t/t3202-show-branch.sh
+++ b/t/t3202-show-branch.sh
@@ -221,4 +221,22 @@ test_expect_success 'fatal descriptions on non-existent branch' '
 	test_cmp expect actual
 '
 
+test_expect_success 'error descriptions on orphan branch' '
+	test_when_finished git worktree remove -f wt &&
+	git worktree add wt --detach &&
+	git -C wt checkout --orphan orphan-branch &&
+	test_branch_op_in_wt() {
+		test_orphan_error() {
+			test_must_fail git $* 2>actual &&
+			test_i18ngrep "No commit on branch .orphan-branch. yet.$" actual
+		} &&
+		test_orphan_error -C wt branch $1 $2 &&                # implicit branch
+		test_orphan_error -C wt branch $1 orphan-branch $2 &&  # explicit branch
+		test_orphan_error branch $1 orphan-branch $2           # different worktree
+	} &&
+	test_branch_op_in_wt --edit-description &&
+	test_branch_op_in_wt --set-upstream-to=ne &&
+	test_branch_op_in_wt -c new-branch
+'
+
 test_done
-- 
2.39.0