obsstore: refactor v1 logic to fix 32 byte hash support
Refactor the v1 logic to determine the node parsing based on the flag.
Move the predecessor out of the fixed part and handle it like the other
nodes, removing most of the duplicated code for parsing 20/32 bytes
hashes.
Differential Revision: https://phab.mercurial-scm.org/D8801
== New Features ==
* `hg mv -A` can now be used with `--at-rev`. It behaves just like
`hg cp -A --at-rev`, i.e. it marks the destination as a copy of the
source whether or not the source still exists (but the source must
exist in the parent revision).
== New Experimental Features ==
== Bug Fixes ==
== Backwards Compatibility Changes ==
== Internal API Changes ==