[PATCH 3/4] Support working directory located at root

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

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 "" instead of "/".

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 <pclouds@gmail.com>
---
 I said I would have code change for DOS drive too. But I take it back.
 Supporting GIT_DIR=C:\.git might be easy, GIT_DIR=C:.git is not.

 setup.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/setup.c b/setup.c
index b38cbee..4d24a74 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(".");
@@ -427,7 +427,7 @@ const char *setup_git_directory_gently(int *nongit_ok)
 	inside_git_dir = 0;
 	if (!work_tree_env)
 		inside_work_tree = 1;
-	git_work_tree_cfg = xstrndup(cwd, offset);
+	git_work_tree_cfg = xstrndup(cwd, offset ? offset : 1);
 	if (check_repository_format_gently(nongit_ok))
 		return NULL;
 	if (offset == len)
-- 
1.7.0.rc2.182.g3adef