Clean up work-tree handling

The old version of work-tree support was an unholy mess, barely readable,
and not to the point.

For example, why do you have to provide a worktree, when it is not used?
As in "git status".  Now it works.

Another riddle was: if you can have work trees inside the git dir, why
are some programs complaining that they need a work tree?

IOW it is allowed to call

	$ git --git-dir=../ --work-tree=. bla

when you really want to.  In this case, you are both in the git directory
and in the working tree.  So, programs have to actually test for the right
thing, namely if they are inside a working tree, and not if they are
inside a git directory.

Also, GIT_DIR=../.git should behave the same as if no GIT_DIR was
specified, unless there is a repository in the current working directory.
It does now.

The logic to determine if a repository is bare, or has a work tree
(tertium non datur), is this:

--work-tree=bla overrides GIT_WORK_TREE, which overrides core.bare = true,
which overrides core.worktree, which overrides GIT_DIR/.. when GIT_DIR
ends in /.git, which overrides the directory in which .git/ was found.

In related news, a long standing bug was fixed: when in .git/bla/x.git/,
which is a bare repository, git formerly assumed ../.. to be the
appropriate git dir.  This problem was reported by Shawn Pearce to have
caused much pain, where a colleague mistakenly ran "git init" in "/" a
long time ago, and bare repositories just would not work.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-init-db.c

@@ -174,36 +174,7 @@ static void copy_templates(const char *git_dir, int len, const char *template_di
 	closedir(dir);
 }
 
-/*
- * Get the full path to the working tree specified in $GIT_WORK_TREE
- * or NULL if no working tree is specified.
- */
-static const char *get_work_tree(void)
-{
-	const char *git_work_tree;
-	char cwd[PATH_MAX];
-	static char worktree[PATH_MAX];
-
-	git_work_tree = getenv(GIT_WORK_TREE_ENVIRONMENT);
-	if (!git_work_tree)
-		return NULL;
-	if (!getcwd(cwd, sizeof(cwd)))
-		die("Unable to read current working directory");
-	if (chdir(git_work_tree))
-		die("Cannot change directory to specified working tree '%s'",
-			git_work_tree);
-	if (git_work_tree[0] != '/') {
-		if (!getcwd(worktree, sizeof(worktree)))
-			die("Unable to read current working directory");
-		git_work_tree = worktree;
-	}
-	if (chdir(cwd))
-		die("Cannot come back to cwd");
-	return git_work_tree;
-}
-
-static int create_default_files(const char *git_dir, const char *git_work_tree,
-	const char *template_path)
+static int create_default_files(const char *git_dir, const char *template_path)
 {
 	unsigned len = strlen(git_dir);
 	static char path[PATH_MAX];
@@ -282,16 +253,16 @@ static int create_default_files(const char *git_dir, const char *git_work_tree,
 	}
 	git_config_set("core.filemode", filemode ? "true" : "false");
 
-	if (is_bare_repository() && !git_work_tree) {
+	if (is_bare_repository())
 		git_config_set("core.bare", "true");
-	}
 	else {
+		const char *work_tree = get_git_work_tree();
 		git_config_set("core.bare", "false");
 		/* allow template config file to override the default */
 		if (log_all_ref_updates == -1)
 		    git_config_set("core.logallrefupdates", "true");
-		if (git_work_tree)
-			git_config_set("core.worktree", git_work_tree);
+		if (work_tree != git_work_tree_cfg)
+			git_config_set("core.worktree", work_tree);
 	}
 	return reinit;
 }
@@ -308,7 +279,6 @@ static const char init_db_usage[] =
 int cmd_init_db(int argc, const char **argv, const char *prefix)
 {
 	const char *git_dir;
-	const char *git_work_tree;
 	const char *sha1_dir;
 	const char *template_dir = NULL;
 	char *path;
@@ -329,7 +299,11 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
 			usage(init_db_usage);
 	}
 
-	git_work_tree = get_work_tree();
+	git_work_tree_cfg = xcalloc(PATH_MAX, 1);
+	if (!getcwd(git_work_tree_cfg, PATH_MAX))
+		die ("Cannot access current working directory.");
+	if (access(get_git_work_tree(), X_OK))
+		die ("Cannot access work tree '%s'", get_git_work_tree());
 
 	/*
 	 * Set up the default .git directory contents
@@ -346,7 +320,7 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
 	 */
 	check_repository_format();
 
-	reinit = create_default_files(git_dir, git_work_tree, template_dir);
+	reinit = create_default_files(git_dir, template_dir);
 
 	/*
 	 * And set up the object store.

builtin-ls-files.c

@@ -469,9 +469,11 @@ int cmd_ls_files(int argc, const char **argv, const char *prefix)
 		break;
 	}
 
-	if (require_work_tree &&
-			(!is_inside_work_tree() || is_inside_git_dir()))
-		die("This operation must be run in a work tree");
+	if (require_work_tree && !is_inside_work_tree()) {
+		const char *work_tree = get_git_work_tree();
+		if (!work_tree || chdir(work_tree))
+			die("This operation must be run in a work tree");
+	}
 
 	pathspec = get_pathspec(prefix, argv + i);
 

builtin-rev-parse.c

@@ -321,6 +321,13 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 			}
 			if (!strcmp(arg, "--show-cdup")) {
 				const char *pfx = prefix;
+				if (!is_inside_work_tree()) {
+					const char *work_tree =
+						get_git_work_tree();
+					if (work_tree)
+						printf("%s\n", work_tree);
+					continue;
+				}
 				while (pfx) {
 					pfx = strchr(pfx, '/');
 					if (pfx) {

cache.h

@@ -208,13 +208,15 @@ enum object_type {
 extern int is_bare_repository_cfg;
 extern int is_bare_repository(void);
 extern int is_inside_git_dir(void);
+extern char *git_work_tree_cfg;
 extern int is_inside_work_tree(void);
 extern const char *get_git_dir(void);
 extern char *get_object_directory(void);
 extern char *get_refs_directory(void);
 extern char *get_index_file(void);
 extern char *get_graft_file(void);
 extern int set_git_dir(const char *path);
+extern const char *get_git_work_tree(void);
 
 #define ALTERNATE_DB_ENVIRONMENT "GIT_ALTERNATE_OBJECT_DIRECTORIES"
 

environment.c

@@ -35,6 +35,10 @@ int pager_in_use;
 int pager_use_color = 1;
 int auto_crlf = 0;	/* 1: both ways, -1: only when adding git objects */
 
+/* This is set by setup_git_dir_gently() and/or git_default_config() */
+char *git_work_tree_cfg;
+static const char *work_tree;
+
 static const char *git_dir;
 static char *git_object_dir, *git_index_file, *git_refs_dir, *git_graft_file;
 
@@ -62,15 +66,8 @@ static void setup_git_env(void)
 
 int is_bare_repository(void)
 {
-	const char *dir, *s;
-	if (0 <= is_bare_repository_cfg)
-		return is_bare_repository_cfg;
-
-	dir = get_git_dir();
-	if (!strcmp(dir, DEFAULT_GIT_DIR_ENVIRONMENT))
-		return 0;
-	s = strrchr(dir, '/');
-	return !s || strcmp(s + 1, DEFAULT_GIT_DIR_ENVIRONMENT);
+	/* if core.bare is not 'false', let's see if there is a work tree */
+	return is_bare_repository_cfg && !get_git_work_tree();
 }
 
 const char *get_git_dir(void)
@@ -80,6 +77,26 @@ const char *get_git_dir(void)
 	return git_dir;
 }
 
+const char *get_git_work_tree(void)
+{
+	static int initialized = 0;
+	if (!initialized) {
+		work_tree = getenv(GIT_WORK_TREE_ENVIRONMENT);
+		/* core.bare = true overrides implicit and config work tree */
+		if (!work_tree && is_bare_repository_cfg < 1) {
+			work_tree = git_work_tree_cfg;
+			/* make_absolute_path also normalizes the path */
+			if (work_tree && !is_absolute_path(work_tree))
+				work_tree = xstrdup(make_absolute_path(git_path(work_tree)));
+		} else if (work_tree)
+			work_tree = xstrdup(make_absolute_path(work_tree));
+		initialized = 1;
+		if (work_tree)
+			is_bare_repository_cfg = 0;
+	}
+	return work_tree;
+}
+
 char *get_object_directory(void)
 {
 	if (!git_object_dir)

git-sh-setup.sh

@@ -59,8 +59,7 @@ cd_to_toplevel () {
 }
 
 require_work_tree () {
-	test $(git rev-parse --is-inside-work-tree) = true &&
-	test $(git rev-parse --is-inside-git-dir) = false ||
+	test $(git rev-parse --is-inside-work-tree) = true ||
 	die "fatal: $0 cannot be used without a working tree."
 }
 

git.c

@@ -272,9 +272,14 @@ static int run_command(struct cmd_struct *p, int argc, const char **argv)
 		prefix = setup_git_directory();
 	if (p->option & USE_PAGER)
 		setup_pager();
-	if ((p->option & NEED_WORK_TREE) &&
-	    (!is_inside_work_tree() || is_inside_git_dir()))
-		die("%s must be run in a work tree", p->cmd);
+	if (p->option & NEED_WORK_TREE) {
+		const char *work_tree = get_git_work_tree();
+		const char *git_dir = get_git_dir();
+		if (!is_absolute_path(git_dir))
+			set_git_dir(make_absolute_path(git_dir));
+		if (!work_tree || chdir(work_tree))
+			die("%s must be run in a work tree", p->cmd);
+	}
 	trace_argv_printf(argv, argc, "trace: built-in: git");
 
 	status = p->fn(argc, argv, prefix);