Merge branch 'jc/branch-in-use-error-message'

"git branch -f X" to repoint the branch X said that X was "checked
out" in another worktree, even when branch X was not and instead
being bisected or rebased.  The message was reworded to say the
branch was "in use".

* jc/branch-in-use-error-message:
  branch: update the message to refuse touching a branch in-use
diff --git a/branch.c b/branch.c
index cdf70b0..3e4684f 100644
--- a/branch.c
+++ b/branch.c
@@ -471,7 +471,7 @@
 
 	if ((path = branch_checked_out(ref->buf)))
 		die(_("cannot force update the branch '%s' "
-		      "checked out at '%s'"),
+		      "used by worktree at '%s'"),
 		    ref->buf + strlen("refs/heads/"), path);
 
 	return 1;
diff --git a/t/t2407-worktree-heads.sh b/t/t2407-worktree-heads.sh
index 019a40d..469443d 100755
--- a/t/t2407-worktree-heads.sh
+++ b/t/t2407-worktree-heads.sh
@@ -58,7 +58,7 @@
 	git -C wt-4 bisect good wt-1 &&
 
 	test_must_fail git branch -f wt-4 HEAD 2>err &&
-	grep "cannot force update the branch '\''wt-4'\'' checked out at.*wt-4" err
+	grep "cannot force update the branch '\''wt-4'\'' used by worktree at.*wt-4" err
 '
 
 test_expect_success !SANITIZE_LEAK 'refuse to overwrite: worktree in rebase (apply)' '
@@ -68,7 +68,7 @@
 	test_must_fail git -C wt-2 rebase --apply conflict-2 &&
 
 	test_must_fail git branch -f wt-2 HEAD 2>err &&
-	grep "cannot force update the branch '\''wt-2'\'' checked out at.*wt-2" err
+	grep "cannot force update the branch '\''wt-2'\'' used by worktree at.*wt-2" err
 '
 
 test_expect_success !SANITIZE_LEAK 'refuse to overwrite: worktree in rebase (merge)' '
@@ -78,7 +78,7 @@
 	test_must_fail git -C wt-2 rebase conflict-2 &&
 
 	test_must_fail git branch -f wt-2 HEAD 2>err &&
-	grep "cannot force update the branch '\''wt-2'\'' checked out at.*wt-2" err
+	grep "cannot force update the branch '\''wt-2'\'' used by worktree at.*wt-2" err
 '
 
 test_expect_success !SANITIZE_LEAK 'refuse to overwrite: worktree in rebase with --update-refs' '
@@ -90,7 +90,7 @@
 	for i in 3 4
 	do
 		test_must_fail git branch -f can-be-updated HEAD 2>err &&
-		grep "cannot force update the branch '\''can-be-updated'\'' checked out at.*wt-3" err ||
+		grep "cannot force update the branch '\''can-be-updated'\'' used by worktree at.*wt-3" err ||
 			return 1
 	done
 '
@@ -150,7 +150,7 @@
 	for i in 1 2
 	do
 		test_must_fail git branch -f fake-$i HEAD 2>err &&
-		grep "cannot force update the branch '\''fake-$i'\'' checked out at" err ||
+		grep "cannot force update the branch '\''fake-$i'\'' used by worktree at" err ||
 			return 1
 	done
 '