+So, pm handling specifics:
+
+strategy is to avoid making needless pseudomerges
+pseudomerges that exist will be preserved
+(by being included in will-overwrite)
+
+This is good because the presence of a pseudomerge means we know we
+want to keep it; and that allows explicit control over history detail
+level.
+
+It does mean we must avoid making the pseudomerges unnecessarily.
+They should be made just before (ideally, part of) dgit push.
+
+1. git-debrebase [-i etc.]
+
+ should:
+ check for will-overwrite
+ if is already a will-overwrite, fine, do no more
+ if not:
+
+ check our origin branch exists and we are ff from it
+ if not fail
+
+ check our other might-be-pushed to branches
+ check we are ff from them
+ if not fail
+
+ set will-overwrite to something which is ff from
+ all above branches
+
+ we use our tip, as discussed above
+ (optionally, can use some other commit which is ff
+ from all of the above, eg one of them)
+
+N. git-debrebase [--noop-ok] record-ffq-prev
+
+ does what is described above
+
+2. git-debrebase [--noop-ok] stitch
+
+ makes pseudomerge with will-overwrite
+ deletes will-overwrite
+
+ we will teach dgit to do
+ git-debrebase stitch
+
+3. git-debrebase push
+
+ like git push only does stitch first
+ ??? command line parsing!
+
+4. git-debrebase release
+
+ stiches, finalises changelog, signs tags, pushes everything
+ for the future, when there is some automatic builder
+
+will-overwrite for each ref
+ refs/heads/FOO
+is
+ refs/ffq-prev/FOO
+
+========================================
+