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>

1 files changed, 127 insertions, 152 deletions

diff --git a/setup.c b/setup.c
index b54d65fd0..3653092ab 100644
--- a/setup.c
+++ b/setup.c
@@ -1,4 +1,8 @@
 #include "cache.h"
+#include "dir.h"
+
+static int inside_git_dir = -1;
+static int inside_work_tree = -1;
 
 const char *prefix_path(const char *prefix, int len, const char *path)
 {
@@ -170,100 +174,89 @@ static int is_git_directory(const char *suspect)
 	return 1;
 }
 
-static int inside_git_dir = -1;
-
 int is_inside_git_dir(void)
 {
-	if (inside_git_dir >= 0)
-		return inside_git_dir;
-	die("BUG: is_inside_git_dir called before setup_git_directory");
+	if (inside_git_dir < 0)
+		inside_git_dir = is_inside_dir(get_git_dir());
+	return inside_git_dir;
 }
 
-static int inside_work_tree = -1;
-
 int is_inside_work_tree(void)
 {
-	if (inside_git_dir >= 0)
-		return inside_work_tree;
-	die("BUG: is_inside_work_tree called before setup_git_directory");
+	if (inside_work_tree < 0)
+		inside_work_tree = is_inside_dir(get_git_work_tree());
+	return inside_work_tree;
 }
 
-static char *gitworktree_config;
-
-static int git_setup_config(const char *var, const char *value)
+/*
+ * If no worktree was given, and we are outside of a default work tree,
+ * now is the time to set it.
+ *
+ * In other words, if the user calls git with something like
+ *
+ *	git --git-dir=/some/where/else/.git bla
+ *
+ * default to /some/where/else as working directory; if the specified
+ * git-dir does not end in "/.git", the cwd is used as working directory.
+ */
+const char *set_work_tree(const char *dir)
 {
-	if (!strcmp(var, "core.worktree")) {
-		if (gitworktree_config)
-			strlcpy(gitworktree_config, value, PATH_MAX);
-		return 0;
+	char dir_buffer[PATH_MAX];
+	static char buffer[PATH_MAX + 1], *rel = NULL;
+	int len, postfix_len = strlen(DEFAULT_GIT_DIR_ENVIRONMENT) + 1;
+
+	/* strip the variable 'dir' of the postfix "/.git" if it has it */
+	len = strlen(dir);
+	if (len > postfix_len && !strcmp(dir + len - postfix_len,
+				"/" DEFAULT_GIT_DIR_ENVIRONMENT)) {
+			strncpy(dir_buffer, dir, len - postfix_len);
+
+		/* are we inside the default work tree? */
+		rel = get_relative_cwd(buffer, sizeof(buffer), dir_buffer);
+	}
+	/* if rel is set, the cwd is _not_ the current working tree */
+	if (rel && *rel) {
+		if (!is_absolute_path(dir))
+			set_git_dir(make_absolute_path(dir));
+		dir = dir_buffer;
+		chdir(dir);
+		strcat(rel, "/");
+		inside_git_dir = 0;
+	} else {
+		rel = NULL;
+		dir = getcwd(buffer, sizeof(buffer));
 	}
-	return git_default_config(var, value);
+	git_work_tree_cfg = xstrdup(dir);
+	inside_work_tree = 1;
+
+	return rel;
 }
 
+/*
+ * We cannot decide in this function whether we are in the work tree or
+ * not, since the config can only be read _after_ this function was called.
+ */
 const char *setup_git_directory_gently(int *nongit_ok)
 {
+	const char *work_tree_env = getenv(GIT_WORK_TREE_ENVIRONMENT);
 	static char cwd[PATH_MAX+1];
-	char worktree[PATH_MAX+1], gitdir[PATH_MAX+1];
-	const char *gitdirenv, *gitworktree;
-	int wt_rel_gitdir = 0;
+	const char *gitdirenv;
+	int len, offset;
 
+	/*
+	 * If GIT_DIR is set explicitly, we're not going
+	 * to do any discovery, but we still do repository
+	 * validation.
+	 */
 	gitdirenv = getenv(GIT_DIR_ENVIRONMENT);
-	if (!gitdirenv) {
-		int len, offset;
-
-		if (!getcwd(cwd, sizeof(cwd)-1))
-			die("Unable to read current working directory");
-
-		offset = len = strlen(cwd);
-		for (;;) {
-			if (is_git_directory(".git"))
-				break;
-			if (offset == 0) {
-				offset = -1;
-				break;
-			}
-			chdir("..");
-			while (cwd[--offset] != '/')
-				; /* do nothing */
-		}
-
-		if (offset >= 0) {
-			inside_work_tree = 1;
-			git_config(git_default_config);
-			if (offset == len) {
-				inside_git_dir = 0;
-				return NULL;
-			}
-
-			cwd[len++] = '/';
-			cwd[len] = '\0';
-			inside_git_dir = !prefixcmp(cwd + offset + 1, ".git/");
-			return cwd + offset + 1;
-		}
-
-		if (chdir(cwd))
-			die("Cannot come back to cwd");
-		if (!is_git_directory(".")) {
-			if (nongit_ok) {
-				*nongit_ok = 1;
-				return NULL;
-			}
-			die("Not a git repository");
-		}
-		setenv(GIT_DIR_ENVIRONMENT, cwd, 1);
-		gitdirenv = getenv(GIT_DIR_ENVIRONMENT);
-		if (!gitdirenv)
-			die("getenv after setenv failed");
-	}
-
-	if (PATH_MAX - 40 < strlen(gitdirenv)) {
-		if (nongit_ok) {
-			*nongit_ok = 1;
+	if (gitdirenv) {
+		if (PATH_MAX - 40 < strlen(gitdirenv))
+			die("'$%s' too big", GIT_DIR_ENVIRONMENT);
+		if (is_git_directory(gitdirenv)) {
+			if (!work_tree_env)
+				return set_work_tree(gitdirenv);
 			return NULL;
 		}
-		die("$%s too big", GIT_DIR_ENVIRONMENT);
-	}
-	if (!is_git_directory(gitdirenv)) {
 		if (nongit_ok) {
 			*nongit_ok = 1;
 			return NULL;
@@ -273,92 +266,53 @@ const char *setup_git_directory_gently(int *nongit_ok)
 
 	if (!getcwd(cwd, sizeof(cwd)-1))
 		die("Unable to read current working directory");
-	if (chdir(gitdirenv)) {
-		if (nongit_ok) {
-			*nongit_ok = 1;
-			return NULL;
-		}
-		die("Cannot change directory to $%s '%s'",
-			GIT_DIR_ENVIRONMENT, gitdirenv);
-	}
-	if (!getcwd(gitdir, sizeof(gitdir)-1))
-		die("Unable to read current working directory");
-	if (chdir(cwd))
-		die("Cannot come back to cwd");
 
 	/*
-	 * In case there is a work tree we may change the directory,
-	 * therefore make GIT_DIR an absolute path.
+	 * Test in the following order (relative to the cwd):
+	 * - .git/
+	 * - ./ (bare)
+	 * - ../.git/
+	 * - ../ (bare)
+	 * - ../../.git/
+	 *   etc.
 	 */
-	if (gitdirenv[0] != '/') {
-		setenv(GIT_DIR_ENVIRONMENT, gitdir, 1);
-		gitdirenv = getenv(GIT_DIR_ENVIRONMENT);
-		if (!gitdirenv)
-			die("getenv after setenv failed");
-		if (PATH_MAX - 40 < strlen(gitdirenv)) {
-			if (nongit_ok) {
-				*nongit_ok = 1;
-				return NULL;
-			}
-			die("$%s too big after expansion to absolute path",
-				GIT_DIR_ENVIRONMENT);
-		}
-	}
-
-	strcat(cwd, "/");
-	strcat(gitdir, "/");
-	inside_git_dir = !prefixcmp(cwd, gitdir);
-
-	gitworktree = getenv(GIT_WORK_TREE_ENVIRONMENT);
-	if (!gitworktree) {
-		gitworktree_config = worktree;
-		worktree[0] = '\0';
-	}
-	git_config(git_setup_config);
-	if (!gitworktree) {
-		gitworktree_config = NULL;
-		if (worktree[0])
-			gitworktree = worktree;
-		if (gitworktree && gitworktree[0] != '/')
-			wt_rel_gitdir = 1;
-	}
-
-	if (wt_rel_gitdir && chdir(gitdirenv))
-		die("Cannot change directory to $%s '%s'",
-			GIT_DIR_ENVIRONMENT, gitdirenv);
-	if (gitworktree && chdir(gitworktree)) {
-		if (nongit_ok) {
-			if (wt_rel_gitdir && chdir(cwd))
-				die("Cannot come back to cwd");
-			*nongit_ok = 1;
+	offset = len = strlen(cwd);
+	for (;;) {
+		if (is_git_directory(DEFAULT_GIT_DIR_ENVIRONMENT))
+			break;
+		if (is_git_directory(".")) {
+			inside_git_dir = 1;
+			if (!work_tree_env)
+				inside_work_tree = 0;
+			setenv(GIT_DIR_ENVIRONMENT, ".", 1);
 			return NULL;
 		}
-		if (wt_rel_gitdir)
-			die("Cannot change directory to working tree '%s'"
-				" from $%s", gitworktree, GIT_DIR_ENVIRONMENT);
-		else
-			die("Cannot change directory to working tree '%s'",
-				gitworktree);
-	}
-	if (!getcwd(worktree, sizeof(worktree)-1))
-		die("Unable to read current working directory");
-	strcat(worktree, "/");
-	inside_work_tree = !prefixcmp(cwd, worktree);
-
-	if (gitworktree && inside_work_tree && !prefixcmp(worktree, gitdir) &&
-	    strcmp(worktree, gitdir)) {
-		inside_git_dir = 0;
+		chdir("..");
+		do {
+			if (!offset) {
+				if (nongit_ok) {
+					if (chdir(cwd))
+						die("Cannot come back to cwd");
+					*nongit_ok = 1;
+					return NULL;
+				}
+				die("Not a git repository");
+			}
+		} while (cwd[--offset] != '/');
 	}
 
-	if (!inside_work_tree) {
-		if (chdir(cwd))
-			die("Cannot come back to cwd");
+	inside_git_dir = 0;
+	if (!work_tree_env)
+		inside_work_tree = 1;
+	git_work_tree_cfg = xstrndup(cwd, offset);
+	if (offset == len)
 		return NULL;
-	}
 
-	if (!strcmp(cwd, worktree))
-		return NULL;
-	return cwd+strlen(worktree);
+	/* Make "offset" point to past the '/', and add a '/' at the end */
+	offset++;
+	cwd[len++] = '/';
+	cwd[len] = 0;
+	return cwd + offset;
 }
 
 int git_config_perm(const char *var, const char *value)
@@ -386,6 +340,16 @@ int check_repository_format_version(const char *var, const char *value)
 		repository_format_version = git_config_int(var, value);
 	else if (strcmp(var, "core.sharedrepository") == 0)
 		shared_repository = git_config_perm(var, value);
+	else if (strcmp(var, "core.bare") == 0) {
+		is_bare_repository_cfg = git_config_bool(var, value);
+		if (is_bare_repository_cfg == 1)
+			inside_work_tree = -1;
+	} else if (strcmp(var, "core.worktree") == 0) {
+		if (git_work_tree_cfg)
+			free(git_work_tree_cfg);
+		git_work_tree_cfg = xstrdup(value);
+		inside_work_tree = -1;
+	}
 	return 0;
 }
 
@@ -402,5 +366,16 @@ const char *setup_git_directory(void)
 {
 	const char *retval = setup_git_directory_gently(NULL);
 	check_repository_format();
+
+	/* If the work tree is not the default one, recompute prefix */
+	if (inside_work_tree < 0) {
+		static char buffer[PATH_MAX + 1];
+		char *rel;
+		if (retval && chdir(retval))
+			die ("Could not jump back into original cwd");
+		rel = get_relative_cwd(buffer, PATH_MAX, get_git_work_tree());
+		return rel && *rel ? strcat(rel, "/") : NULL;
+	}
+
 	return retval;
 }