revlog: guarantee that p1 != null if a non-null parent exists...
revlog: guarantee that p1 != null if a non-null parent exists
This change does not affect the hashing (which already did this
transformation), but can change the log output in the rare case where
this behavior was observed in repositories. The change can simplify
iteration code where regular changesets and merges are distinct
branches.
Differential Revision:
https://phab.mercurial-scm.org/D10150
