Today's way of expressing remote Git repos as contexts

https://github.com/user/repo.git
https://github.com/user/repo.git#
https://github.com/user/repo.git#:
https://github.com/user/repo.git#:dir
https://github.com/user/repo.git#branch_or_tag_or_commit
https://github.com/user/repo.git#branch_or_tag_or_commit:dir

does not allow

• specify both a commit hash and e.g. a branch (as image digests do: $IMAGE_URL:mytag@sha256:cafebabe..)
  • Note importantly: tools such as renovate provide a way to upgrade digests given mytag
• differentiating between a tag or a branch (and a non-full commit)

To permit this I propose to extend this syntax in a somewhat backwards compatible way:

https://github.com/user/repo.git##tag=mytag,branch=main,commit=cafebab,source=/dir

• tag and branch cannot be used together
• commit can be a short commit hash instead of a full one
• note the leading / for source: to keep with uniformity with other csv args
• ## usage (instead of just #) may already exist in the wild (but "unlikely" combined with csv)
• renovate can work with branch or tag (git tags are as mutable as branches) and commit, as with images