Some caveats to branching.
We branch earlier than we really should as a way to encourage stabilization on the master branch.
During that time only milestone-specific changes are allowed into the master and when things are stable (enough) we effectively sync the release branch to the HEAD of the master branch:
$ branchff release-1.3
Once that happens we then open up master to milestone+1 changes and move to the 2 phase cherry-pick model
For emergency patch releases, we may need to branch from an existing tag in order to patch in a single change.
Let's take this example.
We need to make a special patch release from the v1.3.0 tag on the release-1.3 branch.
# Create the new branch and resulting tags, builds, pushes, notifications...
$ anago release-1.3.0
The automatically notified contributor then creates a cherrypick-candidate PR
for the emergency change using the cherry_pick_pull.sh tool.
# Create the new release with the emergency change added only to the v1.3.0
# tag and branch
$ anago --official release-1.3.0