init: fix bug regarding ~/ expansion in init.templateDir

We used to read the init.templateDir setting at builtin/init-db.c using
a git_config() callback that, in turn, called git_config_pathname(). To
simplify the config reading logic at this file and plug a memory leak,
this was replaced by a direct call to git_config_get_value() at
e4de450 ("init: remove git_init_db_config() while fixing leaks",
2021-03-14). However, this function doesn't provide path expanding
semantics, like git_config_pathname() does, so paths with '~/' and
'~user/' are treated literally. This makes 'git init' fail to handle
init.templateDir paths using these constructs:

	$ git config init.templateDir '~/templates_dir'
	$ git init
	'warning: templates not found in ~/templates_dir'

Replace the git_config_get_value() call by git_config_get_pathname(),
which does the '~/' and '~user/' expansions. Also add a regression test.
Note that unlike git_config_get_value(), the config cache does not own
the memory for the path returned by git_config_get_pathname(), so we
must free() it.

Reported on IRC by rkta.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: matheustavares

builtin/init-db.c

@@ -211,8 +211,9 @@ static int create_default_files(const char *template_path,
 	 * values (since we've just potentially changed what's available on
 	 * disk).
 	 */
-	git_config_get_value("init.templatedir", &init_template_dir);
+	git_config_get_pathname("init.templatedir", &init_template_dir);
 	copy_templates(template_path, init_template_dir);
+	free((char *)init_template_dir);
 	git_config_clear();
 	reset_shared_repository();
 	git_config(git_default_config, NULL);

t/t0001-init.sh

@@ -186,21 +186,33 @@ test_expect_success 'init with --template (blank)' '
 	test_path_is_missing template-blank/.git/info/exclude
 '
 
-test_expect_success 'init with init.templatedir set' '
-	mkdir templatedir-source &&
-	echo Content >templatedir-source/file &&
-	test_config_global init.templatedir "${HOME}/templatedir-source" &&
+init_no_templatedir_env () {
 	(
-		mkdir templatedir-set &&
-		cd templatedir-set &&
 		sane_unset GIT_TEMPLATE_DIR &&
 		NO_SET_GIT_TEMPLATE_DIR=t &&
 		export NO_SET_GIT_TEMPLATE_DIR &&
-		git init
-	) &&
+		git init "$1"
+	)
+}
+
+test_expect_success 'init with init.templatedir set' '
+	mkdir templatedir-source &&
+	echo Content >templatedir-source/file &&
+	test_config_global init.templatedir "${HOME}/templatedir-source" &&
+
+	init_no_templatedir_env templatedir-set &&
 	test_cmp templatedir-source/file templatedir-set/.git/file
 '
 
+test_expect_success 'init with init.templatedir using ~ expansion' '
+	mkdir -p templatedir-source &&
+	echo Content >templatedir-source/file &&
+	test_config_global init.templatedir "~/templatedir-source" &&
+
+	init_no_templatedir_env templatedir-expansion &&
+	test_cmp templatedir-source/file templatedir-expansion/.git/file
+'
+
 test_expect_success 'init --bare/--shared overrides system/global config' '
 	test_config_global core.bare false &&
 	test_config_global core.sharedRepository 0640 &&