Fix repository discovery with ceiling_dirs at current directory

git only checks ceiling directories when its search ascends to a parent
directory.  A ceiling directory matching the starting directory will not
prevent git from finding a repository in the starting directory or a
parent directory.  libgit2 handled the former case correctly, but
differed from git in the latter case: given a ceiling directory matching
the starting directory, but no repository at the starting directory,
libgit2 would stop the search at that point rather than finding a
repository in a parent directory.

Test case using git command-line tools:

/tmp$ git init x
Initialized empty Git repository in /tmp/x/.git/
/tmp$ cd x/
/tmp/x$ mkdir subdir
/tmp/x$ cd subdir/
/tmp/x/subdir$ GIT_CEILING_DIRECTORIES=/tmp/x git rev-parse --git-dir
fatal: Not a git repository (or any of the parent directories): .git
/tmp/x/subdir$ GIT_CEILING_DIRECTORIES=/tmp/x/subdir git rev-parse --git-dir
/tmp/x/.git

Fix the testsuite to test this case (in one case fixing a test that
depended on the current behavior), and then fix find_repo to handle this
case correctly.

In the process, simplify and document the logic in find_repo():
- Separate the concepts of "currently checking a .git directory" and
  "number of iterations left before going further counts as a search"
  into two separate variables, in_dot_git and min_iterations.
- Move the logic to handle in_dot_git and append /.git to the top of the
  loop.
- Only search ceiling_dirs and find ceiling_offset after running out of
  min_iterations; since ceiling_offset only tracks the longest matching
  ceiling directory, if ceiling_dirs contained both the current
  directory and a parent directory, this change makes find_repo stop the
  search at the parent directory.

2 files changed, 13 insertions, 2 deletions

diff --git a/tests/repo/discover.c b/tests/repo/discover.c
index 86bd7458f..358daee9f 100644
--- a/tests/repo/discover.c
+++ b/tests/repo/discover.c
@@ -118,12 +118,22 @@ void test_repo_discover__0(void)
 	cl_git_fail(git_repository_discover(&found_path, ALTERNATE_MALFORMED_FOLDER3, 0, ceiling_dirs));
 	cl_assert_equal_i(GIT_ENOTFOUND, git_repository_discover(&found_path, ALTERNATE_NOT_FOUND_FOLDER, 0, ceiling_dirs));
 
+	append_ceiling_dir(&ceiling_dirs_buf, SUB_REPOSITORY_FOLDER_SUB);
+	ceiling_dirs = git_buf_cstr(&ceiling_dirs_buf);
+
+	/* this must pass as ceiling_directories cannot prevent the current
+	 * working directory to be checked */
+	ensure_repository_discover(SUB_REPOSITORY_FOLDER, ceiling_dirs, &sub_repository_path);
+	ensure_repository_discover(SUB_REPOSITORY_FOLDER_SUB, ceiling_dirs, &sub_repository_path);
+	cl_assert_equal_i(GIT_ENOTFOUND, git_repository_discover(&found_path, SUB_REPOSITORY_FOLDER_SUB_SUB, 0, ceiling_dirs));
+	cl_assert_equal_i(GIT_ENOTFOUND, git_repository_discover(&found_path, SUB_REPOSITORY_FOLDER_SUB_SUB_SUB, 0, ceiling_dirs));
+
 	append_ceiling_dir(&ceiling_dirs_buf, SUB_REPOSITORY_FOLDER);
 	ceiling_dirs = git_buf_cstr(&ceiling_dirs_buf);
 
 	//this must pass as ceiling_directories cannot predent the current
 	//working directory to be checked
-	cl_git_pass(git_repository_discover(&found_path, SUB_REPOSITORY_FOLDER, 0, ceiling_dirs));
+	ensure_repository_discover(SUB_REPOSITORY_FOLDER, ceiling_dirs, &sub_repository_path);
 	cl_assert_equal_i(GIT_ENOTFOUND, git_repository_discover(&found_path, SUB_REPOSITORY_FOLDER_SUB, 0, ceiling_dirs));
 	cl_assert_equal_i(GIT_ENOTFOUND, git_repository_discover(&found_path, SUB_REPOSITORY_FOLDER_SUB_SUB, 0, ceiling_dirs));
 	cl_assert_equal_i(GIT_ENOTFOUND, git_repository_discover(&found_path, SUB_REPOSITORY_FOLDER_SUB_SUB_SUB, 0, ceiling_dirs));
diff --git a/tests/repo/open.c b/tests/repo/open.c
index d3d087231..7cdd182a7 100644
--- a/tests/repo/open.c
+++ b/tests/repo/open.c
@@ -196,8 +196,9 @@ void test_repo_open__failures(void)
 		&repo, "attr/sub", GIT_REPOSITORY_OPEN_NO_SEARCH, NULL));
 
 	/* fail with ceiling too low */
-	cl_git_pass(git_buf_joinpath(&ceiling, ceiling.ptr, "sub"));
 	cl_git_fail(git_repository_open_ext(&repo, "attr/sub", 0, ceiling.ptr));
+	cl_git_pass(git_buf_joinpath(&ceiling, ceiling.ptr, "sub"));
+	cl_git_fail(git_repository_open_ext(&repo, "attr/sub/sub", 0, ceiling.ptr));
 
 	/* fail with no repo */
 	cl_git_pass(p_mkdir("alternate", 0777));