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.
This fixes an issue which was detected while using one of the libgit2 bindings [0]. The lack of the trailing forward slash led the name of references returned by git_reference_listall() to be prefixed with a forward slash.
[0]: https://github.com/libgit2/libgit2sharp/pull/108
