setup: rework setup_explicit_git_dir()

This function is the most complex one among the three setup_*
functions because all GIT_DIR, GIT_WORK_TREE, core.worktree and
core.bare are involved.

Because core.worktree is only effective inside
setup_explicit_git_dir() and the extra code in setup_git_directory()
is to handle that. The extra code can now be retired.

Also note that setup_explicit assignment is removed, worktree setting
is no longer decided by get_git_work_tree(). get_git_work_tree() will
be simplified in the next commit.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

setup.c

@@ -208,24 +208,6 @@ int is_inside_work_tree(void)
 	return inside_work_tree;
 }
 
-/*
- * set_work_tree() is only ever called if you set GIT_DIR explicitly.
- * The old behaviour (which we retain here) is to set the work tree root
- * to the cwd, unless overridden by the config, the command line, or
- * GIT_WORK_TREE.
- */
-static const char *set_work_tree(const char *dir)
-{
-	char buffer[PATH_MAX + 1];
-
-	if (!getcwd(buffer, sizeof(buffer)))
-		die ("Could not get the current working directory");
-	git_work_tree_cfg = xstrdup(buffer);
-	inside_work_tree = 1;
-
-	return NULL;
-}
-
 void setup_work_tree(void)
 {
 	const char *work_tree, *git_dir;
@@ -326,40 +308,92 @@ const char *read_gitfile_gently(const char *path)
 }
 
 static const char *setup_explicit_git_dir(const char *gitdirenv,
-				const char *work_tree_env, int *nongit_ok)
+					  char *cwd, int len,
+					  int *nongit_ok)
 {
-	static char buffer[1024 + 1];
-	const char *retval;
+	const char *work_tree_env = getenv(GIT_WORK_TREE_ENVIRONMENT);
+	const char *worktree;
+	char *gitfile;
 
-	if (startup_info)
-		startup_info->setup_explicit = 1;
 	if (PATH_MAX - 40 < strlen(gitdirenv))
 		die("'$%s' too big", GIT_DIR_ENVIRONMENT);
+
+	gitfile = (char*)read_gitfile_gently(gitdirenv);
+	if (gitfile) {
+		gitfile = xstrdup(gitfile);
+		gitdirenv = gitfile;
+	}
+
 	if (!is_git_directory(gitdirenv)) {
 		if (nongit_ok) {
 			*nongit_ok = 1;
+			free(gitfile);
 			return NULL;
 		}
 		die("Not a git repository: '%s'", gitdirenv);
 	}
-	if (!work_tree_env) {
-		retval = set_work_tree(gitdirenv);
-		/* config may override worktree */
-		if (check_repository_format_gently(gitdirenv, nongit_ok))
-			return NULL;
-		return retval;
+
+	if (check_repository_format_gently(gitdirenv, nongit_ok)) {
+		free(gitfile);
+		return NULL;
 	}
-	if (check_repository_format_gently(gitdirenv, nongit_ok))
+
+	/* #3, #7, #11, #15, #19, #23, #27, #31 (see t1510) */
+	if (work_tree_env)
+		set_git_work_tree(work_tree_env);
+	else if (is_bare_repository_cfg > 0) {
+		if (git_work_tree_cfg) /* #22.2, #30 */
+			die("core.bare and core.worktree do not make sense");
+
+		/* #18, #26 */
+		set_git_dir(gitdirenv);
+		free(gitfile);
 		return NULL;
-	retval = get_relative_cwd(buffer, sizeof(buffer) - 1,
-			get_git_work_tree());
-	if (!retval || !*retval)
+	}
+	else if (git_work_tree_cfg) { /* #6, #14 */
+		if (is_absolute_path(git_work_tree_cfg))
+			set_git_work_tree(git_work_tree_cfg);
+		else {
+			char core_worktree[PATH_MAX];
+			if (chdir(gitdirenv))
+				die_errno("Could not chdir to '%s'", gitdirenv);
+			if (chdir(git_work_tree_cfg))
+				die_errno("Could not chdir to '%s'", git_work_tree_cfg);
+			if (!getcwd(core_worktree, PATH_MAX))
+				die_errno("Could not get directory '%s'", git_work_tree_cfg);
+			if (chdir(cwd))
+				die_errno("Could not come back to cwd");
+			set_git_work_tree(core_worktree);
+		}
+	}
+	else /* #2, #10 */
+		set_git_work_tree(".");
+
+	/* set_git_work_tree() must have been called by now */
+	worktree = get_git_work_tree();
+
+	/* both get_git_work_tree() and cwd are already normalized */
+	if (!strcmp(cwd, worktree)) { /* cwd == worktree */
+		set_git_dir(gitdirenv);
+		free(gitfile);
 		return NULL;
-	set_git_dir(make_absolute_path(gitdirenv));
-	if (chdir(work_tree_env) < 0)
-		die_errno ("Could not chdir to '%s'", work_tree_env);
-	strcat(buffer, "/");
-	return retval;
+	}
+
+	if (!prefixcmp(cwd, worktree) &&
+	    cwd[strlen(worktree)] == '/') { /* cwd inside worktree */
+		set_git_dir(make_absolute_path(gitdirenv));
+		if (chdir(worktree))
+			die_errno("Could not chdir to '%s'", worktree);
+		cwd[len++] = '/';
+		cwd[len] = '\0';
+		free(gitfile);
+		return cwd + strlen(worktree) + 1;
+	}
+
+	/* cwd outside worktree */
+	set_git_dir(gitdirenv);
+	free(gitfile);
+	return NULL;
 }
 
 static const char *setup_discovered_git_dir(const char *gitdir,
@@ -441,7 +475,6 @@ static dev_t get_device_or_die(const char *path, const char *prefix)
  */
 static const char *setup_git_directory_gently_1(int *nongit_ok)
 {
-	const char *work_tree_env = getenv(GIT_WORK_TREE_ENVIRONMENT);
 	const char *env_ceiling_dirs = getenv(CEILING_DIRECTORIES_ENVIRONMENT);
 	static char cwd[PATH_MAX+1];
 	const char *gitdirenv, *ret;
@@ -458,6 +491,10 @@ static const char *setup_git_directory_gently_1(int *nongit_ok)
 	if (nongit_ok)
 		*nongit_ok = 0;
 
+	if (!getcwd(cwd, sizeof(cwd)-1))
+		die_errno("Unable to read current working directory");
+	offset = len = strlen(cwd);
+
 	/*
 	 * If GIT_DIR is set explicitly, we're not going
 	 * to do any discovery, but we still do repository
@@ -465,10 +502,7 @@ static const char *setup_git_directory_gently_1(int *nongit_ok)
 	 */
 	gitdirenv = getenv(GIT_DIR_ENVIRONMENT);
 	if (gitdirenv)
-		return setup_explicit_git_dir(gitdirenv, work_tree_env, nongit_ok);
-
-	if (!getcwd(cwd, sizeof(cwd)-1))
-		die_errno("Unable to read current working directory");
+		return setup_explicit_git_dir(gitdirenv, cwd, len, nongit_ok);
 
 	ceil_offset = longest_ancestor_length(cwd, env_ceiling_dirs);
 	if (ceil_offset < 0 && has_dos_drive_prefix(cwd))
@@ -485,7 +519,6 @@ static const char *setup_git_directory_gently_1(int *nongit_ok)
 	 * - ../../.git/
 	 *   etc.
 	 */
-	offset = len = strlen(cwd);
 	one_filesystem = !git_env_bool("GIT_DISCOVERY_ACROSS_FILESYSTEM", 0);
 	if (one_filesystem)
 		current_device = get_device_or_die(".", NULL);
@@ -628,20 +661,5 @@ int check_repository_format(void)
  */
 const char *setup_git_directory(void)
 {
-	const char *retval = setup_git_directory_gently(NULL);
-
-	/* If the work tree is not the default one, recompute prefix */
-	if ((!startup_info || startup_info->setup_explicit) &&
-	    inside_work_tree < 0) {
-		static char buffer[PATH_MAX + 1];
-		char *rel;
-		if (retval && chdir(retval))
-			die_errno ("Could not jump back into original cwd");
-		rel = get_relative_cwd(buffer, PATH_MAX, get_git_work_tree());
-		if (rel && *rel && chdir(get_git_work_tree()))
-			die_errno ("Could not jump to working directory");
-		return rel && *rel ? strcat(rel, "/") : NULL;
-	}
-
-	return retval;
+	return setup_git_directory_gently(NULL);
 }