[PATCH] Support working directory located at root

Git should work regardless where the working directory is located,
even at root. This patch fixes two places where it assumes working
directory always have parent directory.

In setup_git_directory_gently(), when Git goes up to root and finds
.git there, it happily sets worktree to "".

In prefix_path(), loosen the outside repo check a little bit. Usually
when a path XXX is inside worktree /foo, it must be either "/foo", or
"/foo/...". When worktree is simply "/", we can safely ignore the
check: we have a slash at the beginning already.

Not related to worktree, but also set gitdir correctly if a bare repo
is placed (insanely?) at root.

Thanks João Carlos Mendes Luís for pointing out this problem.

Signed-off-by: Nguyễn Thái Ngọc Duy <redacted>
---
 Tell me if this patch is rejected, I'll send another one that makes
 setup_git_* die() if worktree/gitdir is to be set empty. I don't think we
 expect gitdir or worktree to be empty anywhere.

 setup.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/setup.c b/setup.c
index b38cbee..0fcd2fd 100644
--- a/setup.c
+++ b/setup.c

@@ -25,7 +25,7 @@ const char *prefix_path(const char *prefix, int len, const char *path)
 		len = strlen(work_tree);
 		total = strlen(sanitized) + 1;
 		if (strncmp(sanitized, work_tree, len) ||
-		    (sanitized[len] != '\0' && sanitized[len] != '/')) {
+		    (len > 1 && sanitized[len] != '\0' && sanitized[len] != '/')) {
 		error_out:
 			die("'%s' is outside repository", orig);
 		}

@@ -403,7 +403,7 @@ const char *setup_git_directory_gently(int *nongit_ok)
 			if (!work_tree_env)
 				inside_work_tree = 0;
 			if (offset != len) {
-				cwd[offset] = '\0';
+				cwd[offset ? offset : 1] = '\0';
 				set_git_dir(cwd);
 			} else
 				set_git_dir(".");

@@ -427,6 +427,8 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	inside_git_dir = 0;
 	if (!work_tree_env)
 		inside_work_tree = 1;
+	if (offset == 0) /* reached root, set worktree to '/' */
+		offset = 1;
 	git_work_tree_cfg = xstrndup(cwd, offset);
 	if (check_repository_format_gently(nongit_ok))
 		return NULL;

-- 
1.7.0.rc0.54.gd33ef