four dotted decimal, named after the feature release they are updates
to (e.g. "1.8.5.1" was the first maintenance release for "1.8.5"
feature release). These days, maintenance releases are named by
-incrementing the last digit of three-dotted decimal name (e.g. "2.10.2"
-is the second maintenance release for the "2.10" series).
+incrementing the last digit of three-dotted decimal name (e.g. "2.11.1"
+is the first maintenance release for the "2.11" series).
New features never go to the 'maint' branch. This branch is also
merged into "master" to propagate the fixes forward as needed.