libfetchers/git: restore compat with `builtins.fetchGit` from 2.3

Since fb38459d6e58508245553380cccc03c0dbaa1542, each `ref` is appended
with `refs/heads` unless it starts with `refs/` already. This regressed
two use-cases that worked fine before:

* Specifying a commit hash as `ref`: now, if `ref` looks like a commit
  hash it will be directly passed to `git fetch`.

* Specifying a tag without `refs/tags` as prefix: now, the fetcher prepends
  `refs/*` to a ref that doesn't start with `refs/` and doesn't look
  like a commit hash. That way, both a branch and a tag specified in
  `ref` can be fetched.

  The order of preference in git is

  * file in `refs/` (e.g. `HEAD`)
  * file in `refs/tags/`
  * file in `refs/heads` (i.e. a branch)

  After fetching `refs/*`, ref is resolved the same way as git does.

Change-Id: Idd49b97cbdc8c6fdc8faa5a48bef3dec25e4ccc3

0 files changed, 0 insertions, 0 deletions