Refactor git_repository_open with new options

Add a new command `git_repository_open_ext` with extended options
that control how searching for a repository will be done.  The
existing `git_repository_open` and `git_repository_discover` are
reimplemented on top of it.  We may want to change the default
behavior of `git_repository_open` but this commit does not do that.

Improve support for "gitdir" files where the work dir is separate
from the repo and support for the "separate-git-dir" config.  Also,
add support for opening repos created with `git-new-workdir` script
(although I have only confirmed that they can be opened, not that
all functions work correctly).

There are also a few minor changes that came up:

- Fix `git_path_prettify` to allow in-place prettifying.

- Fix `git_path_root` to support backslashes on Win32.  This fix
  should help many repo open/discover scenarios - it is the one
  function called when opening before prettifying the path.

- Tweak `git_config_get_string` to set the "out" pointer to NULL
  if the config value is not found.  Allows some other cleanup.

- Fix a couple places that should have been calling
  `git_repository_config__weakptr` and were not.

- Fix `cl_git_sandbox_init` clar helper to support bare repos.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/errors.c b/src/errors.c
index 70aa641c..aad6c448 100644
--- a/src/errors.c
+++ b/src/errors.c
@@ -92,8 +92,12 @@ const char *git_lasterror(void)
 {
 	char *last_error = GIT_GLOBAL->error.last;
 
-	if (!last_error[0])
+	if (!last_error[0]) {
+		const git_error *err = git_error_last();
+		if (err != NULL)
+			return err->message;
 		return NULL;
+	}
 
 	return last_error;
 }