This is required because if there are projects with the same name
loaded, that have elements in the same path, with the same contents,
they are considered the same, despite actually belonging to different
Projects.

This fixes buildstream issue #795

James Ennis authored Nov 30, 2018 and Jonathan Maw committed Dec 03, 2018

Test required to close #795 - We should be able to build a project which refers
to the same junction twice, but with two different filenames.

_yamlcache.py: Use a project's junction name if present

Closes #795

See merge request !980

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.