rhg: handle null changelog and manifest revisions
Differential Revision: https://phab.mercurial-scm.org/D11650
Create a repo such that the changelog entry refers to a null manifest node:
$ hg init a
$ cd a
$ hg log
$ touch x
$ hg add x
$ hg commit -m "init"
$ hg rm x
$ hg commit -q --amend
$ wc -c < .hg/store/00manifest.i
0
Make sure that the manifest can be read (and is empty):
$ hg --config rhg.on-unsupported=abort files -r .
[1]
Test a null changelog rev, too:
$ hg --config rhg.on-unsupported=abort files -r 0000000000000000000000000000000000000000
[1]