environment: move excludes_file into repo_config_values

The global variable 'excludes_file' is used to track the path to the
global ignore file. If this variable is NULL, 'setup_standard_excludes()'
in 'dir.c' forcefully evaluates and assigns the XDG default path to it.

Continue the libification effort by encapsulating this lazy-loading
fallback logic into a proper getter and moving the variable into
'struct repo_config_values'.

Since 'excludes_file' is a dynamically allocated string, it requires
proper heap memory management. Introduce repo_config_values_clear()
and wire it up in 'repo_clear()' to safely free this memory when a
repository instance is destroyed. Also clean up the heap-allocated
'attributes_file' in this new destructor while we are at it.

Note on transition:

Defensive checks are temporarily retained in both the getter (returning
NULL if uninitialized) and the destructor (bypassing non-the_repository
instances) to maintain bug-to-bug compatibility. These are marked with
NEEDSWORK comments. Future work will track down and fix the offending
callers to eventually replace these shields with stricter BUG()
assertions.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Ayush Chandekar <ayu.chandekar@gmail.com>
Mentored-by: Olamide Caleb Bello <belkid98@gmail.com>
Signed-off-by: Tian Yuchen <cat@malon.dev>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: malon7782

dir.c

@@ -3481,11 +3481,11 @@ static GIT_PATH_FUNC(git_path_info_exclude, "info/exclude")
 
 void setup_standard_excludes(struct dir_struct *dir)
 {
+	const char *excludes_file = repo_excludes_file(the_repository);
+
 	dir->exclude_per_dir = ".gitignore";
 
 	/* core.excludesfile defaulting to $XDG_CONFIG_HOME/git/ignore */
-	if (!excludes_file)
-		excludes_file = xdg_config_home("ignore");
 	if (excludes_file && !access_or_warn(excludes_file, R_OK, 0))
 		add_patterns_from_file_1(dir, excludes_file,
 					 dir->untracked ? &dir->internal.ss_excludes_file : NULL);

environment.c

@@ -57,7 +57,6 @@ enum fsync_method fsync_method = FSYNC_METHOD_DEFAULT;
 enum fsync_component fsync_components = FSYNC_COMPONENTS_DEFAULT;
 char *editor_program;
 char *askpass_program;
-char *excludes_file;
 enum auto_crlf auto_crlf = AUTO_CRLF_FALSE;
 enum eol core_eol = EOL_UNSET;
 int global_conv_flags_eol = CONV_EOL_RNDTRP_WARN;
@@ -134,6 +133,24 @@ int is_bare_repository(void)
 	return is_bare_repository_cfg && !repo_get_work_tree(the_repository);
 }
 
+const char *repo_excludes_file(struct repository *repo)
+{
+	/*
+	 * NEEDSWORK: This is a temporary shield to maintain bug-to-bug
+	 * compatibility during the libification transition.
+	 *
+	 * Once offending callers are properly fixed, this check should
+	 * be upgraded to a BUG() assertion and eventually removed entirely.
+	 */
+	if (!repo || !repo->initialized)
+		return NULL;
+
+	if (!repo_config_values(repo)->excludes_file)
+		repo_config_values(repo)->excludes_file = xdg_config_home("ignore");
+
+	return repo_config_values(repo)->excludes_file;
+}
+
 int have_git_dir(void)
 {
 	return startup_info->have_repository
@@ -461,8 +478,8 @@ int git_default_core_config(const char *var, const char *value,
 	}
 
 	if (!strcmp(var, "core.excludesfile")) {
-		FREE_AND_NULL(excludes_file);
-		return git_config_pathname(&excludes_file, var, value);
+		FREE_AND_NULL(cfg->excludes_file);
+		return git_config_pathname(&cfg->excludes_file, var, value);
 	}
 
 	if (!strcmp(var, "core.whitespace")) {
@@ -715,6 +732,7 @@ int git_default_config(const char *var, const char *value,
 void repo_config_values_init(struct repo_config_values *cfg)
 {
 	cfg->attributes_file = NULL;
+	cfg->excludes_file = NULL;
 	cfg->apply_sparse_checkout = 0;
 	cfg->branch_track = BRANCH_TRACK_REMOTE;
 	cfg->trust_ctime = 1;
@@ -726,3 +744,22 @@ void repo_config_values_init(struct repo_config_values *cfg)
 	cfg->sparse_expect_files_outside_of_patterns = 0;
 	cfg->warn_on_object_refname_ambiguity = 1;
 }
+
+void repo_config_values_clear(struct repository *repo)
+{
+	struct repo_config_values *cfg;
+
+	/*
+	 * NEEDSWORK: Temporary shield to prevent temporary/uninitialized
+	 * submodules from triggering the BUG() at repository.c:59
+	 * during repo_clear(). This should be removed once submodule
+	 * lifecycle and per-repo config support are fully resolved.
+	 */
+	if (repo != the_repository)
+		return;
+
+	cfg = repo_config_values(repo);
+
+	FREE_AND_NULL(cfg->attributes_file);
+	FREE_AND_NULL(cfg->excludes_file);
+}

environment.h

@@ -90,6 +90,7 @@ struct repository;
 struct repo_config_values {
 	/* section "core" config values */
 	char *attributes_file;
+	char *excludes_file;
 	int apply_sparse_checkout;
 	int trust_ctime;
 	int check_stat;
@@ -133,8 +134,19 @@ int git_default_config(const char *, const char *,
 int git_default_core_config(const char *var, const char *value,
 			    const struct config_context *ctx, void *cb);
 
+const char *repo_excludes_file(struct repository *repo);
+
 void repo_config_values_init(struct repo_config_values *cfg);
 
+/*
+ * Frees memory allocated for dynamically loaded configuration values
+ * inside `repo_config_values`.
+ *
+ * As dynamically allocated variables are migrated into this struct,
+ * their FREE_AND_NULL() calls should be appended here.
+ */
+void repo_config_values_clear(struct repository *repo);
+
 /*
  * TODO: All the below state either explicitly or implicitly relies on
  * `the_repository`. We should eventually get rid of these and make the
@@ -208,7 +220,6 @@ extern char *git_log_output_encoding;
 
 extern char *editor_program;
 extern char *askpass_program;
-extern char *excludes_file;
 
 /*
  * The character that begins a commented line in user-editable file

repository.c

@@ -388,6 +388,7 @@ void repo_clear(struct repository *repo)
 	FREE_AND_NULL(repo->parsed_objects);
 
 	repo_settings_clear(repo);
+	repo_config_values_clear(repo);
 
 	if (repo->config) {
 		git_configset_clear(repo->config);