Merge branch 'rs/branch-allow-deleting-dangling' into maint

"git branch -D <branch>" used to refuse to remove a broken branch
ref that points at a missing commit, which has been corrected.

* rs/branch-allow-deleting-dangling:
  branch: allow deleting dangling branches with --force

Author: gitster

Documentation/git-branch.txt

@@ -118,7 +118,8 @@ OPTIONS
 	Reset <branchname> to <startpoint>, even if <branchname> exists
 	already. Without `-f`, 'git branch' refuses to change an existing branch.
 	In combination with `-d` (or `--delete`), allow deleting the
-	branch irrespective of its merged status. In combination with
+	branch irrespective of its merged status, or whether it even
+	points to a valid commit. In combination with
 	`-m` (or `--move`), allow renaming the branch even if the new
 	branch name already exists, the same applies for `-c` (or `--copy`).
 

builtin/branch.c

@@ -168,7 +168,7 @@ static int check_branch_commit(const char *branchname, const char *refname,
 			       int kinds, int force)
 {
 	struct commit *rev = lookup_commit_reference(the_repository, oid);
-	if (!rev) {
+	if (!force && !rev) {
 		error(_("Couldn't look up commit object for '%s'"), refname);
 		return -1;
 	}

t/t3200-branch.sh

@@ -1272,6 +1272,19 @@ test_expect_success 'attempt to delete a branch merged to its base' '
 	test_must_fail git branch -d my10
 '
 
+test_expect_success 'branch --delete --force removes dangling branch' '
+	git checkout main &&
+	test_commit unstable &&
+	hash=$(git rev-parse HEAD) &&
+	objpath=$(echo $hash | sed -e "s|^..|.git/objects/&/|") &&
+	git branch --no-track dangling &&
+	mv $objpath $objpath.x &&
+	test_when_finished "mv $objpath.x $objpath" &&
+	git branch --delete --force dangling &&
+	git for-each-ref refs/heads/dangling >actual &&
+	test_must_be_empty actual
+'
+
 test_expect_success 'use --edit-description' '
 	write_script editor <<-\EOF &&
 		echo "New contents" >"$1"