Track of git tags and save them to reproduce minimum shallow repository

Description

This is a proposal to solve #487 (closed) in a reproducible way. This is marked as WIP because there is still some work to do. But I would like to feedback about the idea.

Instead of tag information being fetched which can change with time, they are tracked and saved in the projects.refs/.bst. Then we re-tag automatically the closest tag so that git describe works and is reproducible.

The commands are inspired from script $1731497. There are details I skipped that might be important to use.

This supports all combination of --first-parent and --tags parameters. This is why there are potentially several tags stored.

This merge request, when approved, will close: #487 (closed)

---