init-db: document existing bug with core.bare in template config

The comments in create_default_files() talks about reading config from
the config file in the specified `--templates` directory, which leads to
the question of whether core.bare could be set in such a config file and
thus whether the code is doing the right thing.  It turns out, that it
doesn't; it unconditionally ignores core.bare in the config file in any
--templates directory.  It is not clear to me that fixing it can be done
within this function; it seems to occur too late:
  * create_default_files() is called by init_db()
  * init_db() is called by both builtin/{clone.c,init-db.c}
  * both callers of init_db() call set_git_work_tree() before init_db()
and in order to actual affect whether a repository is bear, we'd need to
somewhere reset these values, not just the is_bare_repository_cfg
setting.

I do not want to open this can of worms at this time; I'm trying to
clean up some headers, for which I need to move some functions, for
which I need to clean up some globals, and that's far enough down the
rabbit hole.  So, simply document the issue with a careful TODO comment
and a few testcases.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/init-db.c

@@ -231,9 +231,36 @@ static int create_default_files(const char *template_path,
 	 * We must make sure command-line options continue to override any
 	 * values we might have just re-read from the config.
 	 */
-	is_bare_repository_cfg = init_is_bare_repository || !work_tree;
 	if (init_shared_repository != -1)
 		set_shared_repository(init_shared_repository);
+	/*
+	 * TODO: heed core.bare from config file in templates if no
+	 *       command-line override given
+	 */
+	is_bare_repository_cfg = init_is_bare_repository || !work_tree;
+	/* TODO (continued):
+	 *
+	 * Unfortunately, the line above is equivalent to
+	 *    is_bare_repository_cfg = !work_tree;
+	 * which ignores the config entirely even if no `--[no-]bare`
+	 * command line option was present.
+	 *
+	 * To see why, note that before this function, there was this call:
+	 *    init_is_bare_repository = is_bare_repository()
+	 * expanding the right hand side:
+	 *                 = is_bare_repository_cfg && !get_git_work_tree()
+	 *                 = is_bare_repository_cfg && !work_tree
+	 * note that the last simplification above is valid because nothing
+	 * calls repo_init() or set_git_work_tree() between any of the
+	 * relevant calls in the code, and thus the !get_git_work_tree()
+	 * calls will return the same result each time.  So, what we are
+	 * interested in computing is the right hand side of the line of
+	 * code just above this comment:
+	 *     init_is_bare_repository || !work_tree
+	 *        = is_bare_repository_cfg && !work_tree || !work_tree
+	 *        = !work_tree
+	 * because "A && !B || !B == !B" for all boolean values of A & B.
+	 */
 
 	/*
 	 * We would have created the above under user's umask -- under

t/t1301-shared-repo.sh

@@ -52,6 +52,28 @@ test_expect_success 'shared=all' '
 	test 2 = $(git config core.sharedrepository)
 '
 
+test_expect_failure 'template can set core.bare' '
+	test_when_finished "rm -rf subdir" &&
+	test_when_finished "rm -rf templates" &&
+	test_config core.bare true &&
+	umask 0022 &&
+	mkdir -p templates/ &&
+	cp .git/config templates/config &&
+	git init --template=templates subdir &&
+	test_path_exists subdir/HEAD
+'
+
+test_expect_success 'template can set core.bare but overridden by command line' '
+	test_when_finished "rm -rf subdir" &&
+	test_when_finished "rm -rf templates" &&
+	test_config core.bare true &&
+	umask 0022 &&
+	mkdir -p templates/ &&
+	cp .git/config templates/config &&
+	git init --no-bare --template=templates subdir &&
+	test_path_exists subdir/.git/HEAD
+'
+
 test_expect_success POSIXPERM 'update-server-info honors core.sharedRepository' '
 	: > a1 &&
 	git add a1 &&

t/t5606-clone-options.sh

@@ -120,6 +120,16 @@ test_expect_success 'prefers -c config over --template config' '
 
 '
 
+test_expect_failure 'prefers --template config even for core.bare' '
+
+	template="$TRASH_DIRECTORY/template-with-bare-config" &&
+	mkdir "$template" &&
+	git config --file "$template/config" core.bare true &&
+	git clone "--template=$template" parent clone-bare-config &&
+	test "$(git -C clone-bare-config config --local core.bare)" = "true" &&
+	test_path_is_file clone-bare-config/HEAD
+'
+
 test_expect_success 'prefers config "clone.defaultRemoteName" over default' '
 
 	test_config_global clone.defaultRemoteName from_config &&