After running conda jobs on tags, the following failed:
https://gitlab.astro-wise.org/omegacen/common/-/pipelines/10844
This was due to the tags created by the MM job not being protected,
but the CONDA_UPLOAD_KEY (set globally by an admin) was.

This has been fixed for the common project: the tags `20*` are now
protected.

This MR adds a bit of documentation to other confused project owners
can understand what's going on.

As requested by Ewout, this environment variable can be set to
trigger the conda build and test jobs in scheduled pipelines.

Since GitLab 13.1 has introduced
[Global CI variables](https://docs.gitlab.com/ee/api/instance_level_ci_variables.html),
there is no need to add them to each project separately anymore.

Teake Nutma authored 4 years ago and Hugo Buddelmeijer committed 4 years ago

This variable can be used for setting the conda package name to the
git branch. If it is left unset, it will default to CI_COMMIT_REF_NAME
with bad characters replace with dots ('.'). The bad characters are
conda-build specific, and are '=@#$%^&*:;"\'\\|<>?/ -'
(see https://github.com/conda/conda-build/blob/ef6e0b5aaa7652d37e8cdf3f461bf987610b89b0/conda_build/metadata.py#L529).

CI_COMMIT_REF_NAME is equal to the name of the branch when no tag is
set, and equal to the name of the tag otherwise.

This is useful for when we'll have multiple jobs on schedules and
we want to run them selectively.

This is adapted from omegacen/common:/toolbox/git_merge_tag.sh.
The behaviour is a bit different though: instead of amending the bump
commit, it is now a seperate commit on the target branch.