This commit adds RELEASING.md guide describing the process of making a new
upstream release and pushing it into Fedora and CentOS Stream 9.
Additionally, a new helper is added to the repository - update-distgit.py.
The purpose of this helper is to simplify work with the dist-git.
Random thoughts:
I decided to left off RHEL 8 because the guide would be full of internal
URLs and tools. I will probably write a similar guide for it and put it
into internal guides.
I decided to just reference the RHEL Developer Guide for CentOS Stream 9.
It's pretty well written and I didn't feel like duplicating the effort.
We should definitely switch to PR-based approach for Fedora and implement
at least some smoke tests. I believe that the current guide is good enough
and we can iterate later.
Signed-off-by: Ondřej Budai <ondrej@budai.cz>
