I recently had to create a branch for an older release in order to issue fixes for it (jaggr-1.1.8). We had moved on since to jaggr-1.2.0-SNAPSHOT so I had to figure out the best way to do it. These are the steps that worked for me at the time.
First, I created a branch called staging-jaggr-1.1.x from the jaggr-1.1.8 tag to stage the change. For some reason this process wouldn’t work if I simply checked out the tag.
git checkout -b staging-jaggr-1.1.x jaggr-1.1.8
Next, I used maven to create the jaggr-1.1.x branch following these maven:release instructions.
mvn release:branch -DbranchName=jaggr-1.1.x -DupdateBranchVersions=true -DupdateWorkingCopyVersions=false
Finally, I deleted the local branch staging-jaggr-1.1.x as well as the remote one that was pushed to the parent project.