charm-build --write-lock-file fails to pick up master branch for interface:ceph-mds

[ajkavanagh]

Checklist

• Confirmed this is an issue with charm-tools, not charmstore-client
• Provide versions of tools used
• Described the feature or ways to replicate the issue

What version am I running?

I ran the following command: snap info charm and got the following ouput:

charm-tools 2.8.3 from PyPi

I am using: Ubuntu 20.04

Issue/Feature

Adding a build.lock file is done with charm-build --log-level DEBUG --write-lock-file …

This creates the build.lock file and records the branch against the git hash for the repository for the layer/interface. However, it's doesn't seem to record a branch for interface:ceph-mds which results in bug #603 if the build.lock is attempted to be build using branches.

I expect/expected the following

I expected the branch refs/heads/master to be recorded against interface:ceph-mds

What I got

    {
      "type": "layer",
      "item": "interface:ceph-mds",
      "url": "https://opendev.org/openstack/charm-interface-ceph-client.git",
      "vcs": null,
      "branch": null,
      "commit": "72245e1d002fb9c65c9574d65b5952275b3411fb"
    },

Contrast with:

    {
      "type": "layer",
      "item": "layer:ceph",
      "url": "https://github.com/openstack/charm-layer-ceph.git",
      "vcs": null,
      "branch": "refs/heads/master",
      "commit": "17d40abd8d9ec3b8c32756ca981c80c4733c016f"
    },

[ajkavanagh]

The reason is fails to pick up the branch is due to interface:ceph-mds being a sub-directory-of-a-git-repository interface/layer which means that when it is copied the .git directory is not copied and so the branch can't be found. A bit of debug gives:

get_branch_for_revision: /home/alex/.cache/charm/2429380/interface/ceph-mds
... got error:  fatal: not a git repository (or any parent up to mount point /)
Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).

where get_branch_for_revision is (with some added debug):

    def get_branch_for_revision(self, dir_, revision=None):
        """Returns None if the revision doesn't match the actual branch name"""
        print("get_branch_for_revision:", dir_)
        if revision is None:
            revision = self.revision
        if not revision:
            print("... no revision?", revision)
            return None
        for cmd in ("git branch --contains {} --format=\"%(refname)\""
                    .format(revision), ):
            try:
                branch = check_output(cmd, cwd=dir_).decode('UTF-8').strip()
                return branch
            except FetchError as e:
                print("... got error: ", e)
                continue
        return None

The fix will have to be to call get_branch_for_revision on the uncopied repository rather than the copied interface/layer. Might be tricky to organise that in the code.