+# usages:
+# git-debrebase launder # prints breakwater tip
+# git-debrebase analyse
+# git-debrebase start # like ffrebase start + debrebase launder
+# git-debrebase new-upstream [-f] UPSTREAM
+# git-debrebase <git-rebase options> # does debrebase start if necessary
+#
+# git-ffrebase start [BASE] # records previous HEAD so it can be overwritten
+# # records base for future git-ffrebase
+# git-ffrebase set-base BASE
+# git-ffrebase <git-rebase options>
+# git-ffrebase finish
+# git-ffrebase status [BRANCH]
+#
+# refs/ffrebase-prev/BRANCH BRANCH may be refs/...; if not it means
+# refs/ffrebase-base/BRANCH refs/heads/BRANCH
+
+