(NB that this definition excludes dependency removals
which have already occurred on our base; these will be
reverted later.)
For each unwanted dependency removal (ie for each such
branch), find the most recent commit which unwantedly removed
(NB that this definition excludes dependency removals
which have already occurred on our base; these will be
reverted later.)
For each unwanted dependency removal (ie for each such
branch), find the most recent commit which unwantedly removed