repo2docker.ref contains HEAD rather than the actual commit ID at the time of creation

[sgaist]

Bug description

When creating an image, if HEAD is used, then the repo2docker.ref label will contain that value which is not really useful. One must start a container and use git to know which commit was used to build the container.

The same goes if --ref is not used, then the ref will be None

Expected behaviour

When HEAD is used, the commit hash should be put it in repo2docker.ref.
Same goes if --ref is not used.

Actual behaviour

repo2docker.ref contains the literal HEAD when --ref HEAD is used.
repo2docker.ref contains the literal None when --ref is not used.

How to reproduce

1. clone a repo2docker repository
2. run repo2docker --no-run --no-push --image-name label-test .
3. docker image inspect label-test -f '{{ index .Config.Labels "repo2docker.ref" }}'
4. See None

Your personal set up

• OS: [linux, OSX]
• Docker version: Docker Desktop 4.25.1 (128006)
• repo2docker version: 2023.06.0+47.g1bb3cba (development installation)

[sgaist]

After having done some testing and gone through the ContentProviders subclasses, I am wondering whether repo2dock.ref should simply contain the value returned by content_id ?