branch: error message deleting a branch in use

Let's update the error message we show when the user tries to delete a
branch which is being used in another worktree, following the guideline
reasoned in 4970bed (branch: update the message to refuse touching a
branch in-use, 2023-07-21).

Signed-off-by: Rubén Justo <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: rjusto

builtin/branch.c

@@ -262,7 +262,7 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 			const char *path;
 			if ((path = branch_checked_out(name))) {
 				error(_("Cannot delete branch '%s' "
-					"checked out at '%s'"),
+					"used by worktree at '%s'"),
 				      bname.buf, path);
 				ret = 1;
 				continue;

t/t3200-branch.sh

@@ -942,7 +942,19 @@ test_expect_success 'test deleting branch without config' '
 test_expect_success 'deleting currently checked out branch fails' '
 	git worktree add -b my7 my7 &&
 	test_must_fail git -C my7 branch -d my7 &&
-	test_must_fail git branch -d my7 &&
+	test_must_fail git branch -d my7 2>actual &&
+	grep "^error: Cannot delete branch .my7. used by worktree at " actual &&
+	rm -r my7 &&
+	git worktree prune
+'
+
+test_expect_success 'deleting in-use branch fails' '
+	git worktree add my7 &&
+	test_commit -C my7 bt7 &&
+	git -C my7 bisect start HEAD HEAD~2 &&
+	test_must_fail git -C my7 branch -d my7 &&
+	test_must_fail git branch -d my7 2>actual &&
+	grep "^error: Cannot delete branch .my7. used by worktree at " actual &&
 	rm -r my7 &&
 	git worktree prune
 '