upgrade: no longer keep all revlogs in memory at any point
Keeping all object open is unsustainable, so we will open them on demand. This
mean opening them multiple times, but this is a lesser evil.
Each revlog consume a small amount of memory (index content, associated nodemap,
etc). While there are few "big" revlog, the sheer amount of small filelog can
become a significant issue memory wise, consuming multiple GB of memory. If you
combines this extra usage with the use of multiprocessing, this usage can
quickly get out of control. This can effectively block the upgrade of larger
repository. This changeset fixes this issue.
demandimport: convert ignored modules from bytes -> str in extensions
The default list of ignored modules are str, and test for bypassing the lazy
import is `module.__name__ in ignores`, so these were effectively NOT ignored.
Most of these date back to the grand byteification in
687b865b95ad, with some
subsequent additions that followed the existing example.
I have no idea if these modules in fact need to bypass lazy importing, but at
least it follows the intent of the code.