+ git checkout master
+ - update the version in configure.ac
+ git log > ChangeLog
+ git commit -a
+ - make absolutely sure checked-out tree is "clean"
+ - if this is an x.y release, then:
+ git checkout -b branch-<version>
+ git tag -a <version>
+ - if this is an x.y.z release, then:
+ git checkout branch-<version> # the x.y parts only
+ git merge master
+ git tag -a <version> # full x.y.z version