Unfortunately, disabling the rust extensions means newer
Mercurial versions no longer have the persistent-nodemap
This means a Mercurial 5.8.1 on RPM-based Linux distributions
will no longer be able to read repositories created
by a Mercurial 5.8 on RPM-based Linux distributions.
This violates the compatibility rules
(see https://www.mercurial-scm.org/wiki/CompatibilityRules ).
For this reason, I have to backout this change.
I'll try to find another solution to the 'hg purge' crashes.