environment: split up concerns of is_bare_repository_cfg

The `is_bare_repository_cfg` variable tracks two different pieces of
information:

  - It tracks whether the user has invoked git with the "--bare" flag,
    which makes us treat any discovered Git repository as if it was a
    bare repository.

  - Otherwise it tracks whether the discovered `the_repository` is bare.

This makes the flag extremely confusing and creates a bit of a challenge
when handling multiple repositories in the same process.

Split up the concerns of this variable into two pieces:

  - `startup_info.force_bare_repository` tracks whether the user has
    passed the "--bare" flag. This is used as a hint to treat newly set
    up repositories as bare regardless of whether or not they have a
    worktree.

  - `struct repository::bare_cfg` tracks whether or not a repository is
    considered bare. This takes into account both whether the user has
    passed "--bare" and the discovered state of the repository itself.

Whether or not a repository is bare is now resolved when checking the
repository's format, and is then later applied to the repository itself
via `apply_repository_format()`.

This enables a subsequent change where we make `is_bare_repository()`
not depend on global state anymore.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/init-db.c

@@ -81,7 +81,7 @@ int cmd_init_db(int argc,
 	const char *template_dir = NULL;
 	char *template_dir_to_free = NULL;
 	unsigned int flags = 0;
-	int bare = is_bare_repository_cfg;
+	int bare = startup_info->force_bare_repository ? 1 : -1;
 	const char *object_format = NULL;
 	const char *ref_format = NULL;
 	const char *initial_branch = NULL;

environment.c

@@ -48,7 +48,6 @@ int has_symlinks = 1;
 int minimum_abbrev = 4, default_abbrev = -1;
 int ignore_case;
 int assume_unchanged;
-int is_bare_repository_cfg = -1; /* unspecified */
 int warn_on_object_refname_ambiguity = 1;
 char *git_commit_encoding;
 char *git_log_output_encoding;
@@ -136,7 +135,7 @@ const char *getenv_safe(struct strvec *argv, const char *name)
 int is_bare_repository(void)
 {
 	/* if core.bare is not 'false', let's see if there is a work tree */
-	return is_bare_repository_cfg && !repo_get_work_tree(the_repository);
+	return the_repository->bare_cfg && !repo_get_work_tree(the_repository);
 }
 
 int have_git_dir(void)
@@ -342,7 +341,7 @@ int git_default_core_config(const char *var, const char *value,
 	}
 
 	if (!strcmp(var, "core.bare")) {
-		is_bare_repository_cfg = git_config_bool(var, value);
+		the_repository->bare_cfg = git_config_bool(var, value);
 		return 0;
 	}
 

environment.h

@@ -147,7 +147,6 @@ void repo_config_values_init(struct repo_config_values *cfg);
  */
 int have_git_dir(void);
 
-extern int is_bare_repository_cfg;
 int is_bare_repository(void);
 
 /* Environment bits from configuration mechanism */

git.c

@@ -255,7 +255,7 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 				*envchanged = 1;
 		} else if (!strcmp(cmd, "--bare")) {
 			char *cwd = xgetcwd();
-			is_bare_repository_cfg = 1;
+			startup_info->force_bare_repository = true;
 			setenv(GIT_DIR_ENVIRONMENT, cwd, 0);
 			free(cwd);
 			setenv(GIT_IMPLICIT_WORK_TREE_ENVIRONMENT, "0", 1);

repository.c

@@ -73,6 +73,7 @@ void initialize_repository(struct repository *repo)
 	ALLOC_ARRAY(repo->index, 1);
 	index_state_init(repo->index, repo);
 	repo->check_deprecated_config = true;
+	repo->bare_cfg = -1;
 	repo_config_values_init(&repo->config_values_private_);
 
 	/*

repository.h

@@ -117,6 +117,13 @@ struct repository {
 	bool worktree_initialized;
 	bool worktree_config_is_bogus;
 
+	/*
+	 * Whether the repository is bare, as set by "core.bare" config or
+	 * inferred during repository discovery. -1 means unset/unknown, 0
+	 * means non-bare, 1 means bare.
+	 */
+	int bare_cfg;
+
 	/*
 	 * Path from the root of the top-level superproject down to this
 	 * repository.  This is only non-NULL if the repository is initialized

setup.c

@@ -795,10 +795,22 @@ static int check_repository_format_gently(const char *gitdir,
 		has_common = 0;
 	}
 
-	if (!has_common) {
-		if (candidate->is_bare != -1)
-			is_bare_repository_cfg = candidate->is_bare;
-	} else {
+	if (startup_info->force_bare_repository) {
+		candidate->is_bare = 1;
+		FREE_AND_NULL(candidate->work_tree);
+	} else if (has_common) {
+		/*
+		 * When sharing a common dir with another repository (e.g. a
+		 * linked worktree), do not let this repository's config
+		 * dictate bareness; it is inherited from the main worktree.
+		 */
+		candidate->is_bare = -1;
+
+		/*
+		 * Furthermore, "core.worktree" is supposed to be ignored when
+		 * we have a commondir configured, unless it comes from the
+		 * per-worktree configuration.
+		 */
 		FREE_AND_NULL(candidate->work_tree);
 	}
 
@@ -1138,7 +1150,7 @@ static const char *setup_explicit_git_dir(struct repository *repo,
 	/* #3, #7, #11, #15, #19, #23, #27, #31 (see t1510) */
 	if (work_tree_env)
 		set_git_work_tree(repo, work_tree_env);
-	else if (is_bare_repository_cfg > 0) {
+	else if (repo_fmt->is_bare > 0) {
 		if (repo_fmt->work_tree) {
 			/* #22.2, #30 */
 			warning("core.bare and core.worktree do not make sense");
@@ -1225,7 +1237,7 @@ static const char *setup_discovered_git_dir(struct repository *repo,
 	}
 
 	/* #16.2, #17.2, #20.2, #21.2, #24, #25, #28, #29 (see t1510) */
-	if (is_bare_repository_cfg > 0) {
+	if (repo_fmt->is_bare > 0) {
 		set_git_dir(repo, gitdir, (offset != cwd->len));
 		if (chdir(cwd->buf))
 			die_errno(_("cannot come back to cwd"));
@@ -1762,6 +1774,7 @@ int apply_repository_format(struct repository *repo,
 		alternate_object_directories = xstrdup_or_null(getenv(ALTERNATE_DB_ENVIRONMENT));
 	}
 
+	repo->bare_cfg = format->is_bare;
 	repo_set_hash_algo(repo, format->hash_algo);
 	repo->objects = odb_new(repo, object_directory,
 				alternate_object_directories);
@@ -2571,7 +2584,7 @@ static int create_default_files(struct repository *repo,
 		repo_settings_set_shared_repository(repo,
 						    init_shared_repository);
 
-	is_bare_repository_cfg = !work_tree;
+	repo->bare_cfg = !work_tree;
 
 	/*
 	 * We would have created the above under user's umask -- under

setup.h

@@ -292,6 +292,12 @@ enum sharedrepo {
 int git_config_perm(const char *var, const char *value);
 
 struct startup_info {
+	/*
+	 * Whether the user is asking us to treat the repository as bare via
+	 * `git --bare`, even if it's not.
+	 */
+	bool force_bare_repository;
+
 	int have_repository;
 	const char *prefix;
 	const char *original_cwd;

worktree.c

@@ -123,7 +123,7 @@ static struct worktree *get_main_worktree(int skip_reading_head)
 	worktree->repo = the_repository;
 	worktree->path = strbuf_detach(&worktree_path, NULL);
 	worktree->is_current = is_current_worktree(worktree);
-	worktree->is_bare = (is_bare_repository_cfg == 1) ||
+	worktree->is_bare = (the_repository->bare_cfg == 1) ||
 		is_bare_repository() ||
 		/*
 		 * When in a secondary worktree we have to also verify if the main