This injects in 2 different tests, 2 different repositories (one with
2 branches and no tag, another with 1 branch and 1 tag). We then check
the snapshot is targetting accordingly those branches/releases.
The hashes computed are explained in the test_loader.org.
This does not cover all the mercurial use cases.
make coverage (outside of venv though, reports nothing in the venv)
reports 76% of coverage, that's a start.
Related T954