It seems that Renovate assumes Git tags for these kind of definitions,
and therefore cannot handle commit refs.
So a custom regex manager is needed, with a way to manually specify the
branch to use, thanks to the `master` vs `main` split.
Many dependencies are installed manually within the Dockerfiles,
where Renovate cannot determine the version numbers by default.
However, through custom matching, the corresponding data sources
can be invoked, and the version number replaced via regex.
