feat(git): added commit hash support to git.ref

[idsulik]

Fixes: #7018

Description
Added commit hash support to git.ref

User facing changes
before: no hash support for git.ref.
after: git.ref supports commit hash.

example:

apiVersion: skaffold/v4beta11
kind: Config
requires:
- git:
    repo: https://github.com/GoogleContainerTools/skaffold
    ref: f386e6c552e83c3a9445fe34442aaed8dd381ab3
    path: examples/multi-config-microservices/leeroy-app
    sync: false

[idsulik]

Hi @ericzzzzzzz ,

I noticed that this pull request has been pending for a while. Is there anything more needed from my side? Please let me know if there are any updates or additional changes required.

Thanks!