Support git-ls syntax for CI cache

Problem to solve

Some users might like to specify cache for files beyond untracked (e.g. ignored). Since untracked already makes use of git ls-files, it makes sense to think to support its syntax to specify which files to be cached.

Target audience

Software Developers, DevOps engineers

Proposal

Support git-ls syntax for CI cache

Links / references

ZD https://gitlab.zendesk.com/agent/tickets/111779