stablerange: rework the debug command to allow for multiple method Similar to what we did for the other debug command related to sorting, we prepare for the arrival of multiple method to produce the result (including simple implementation that are easy to read but do not scale).

deptcache: make sure we warm the dept cache before warming the obsdiscovery The depthcache need to a warmed a bit more agressively

stablesort: add a 'method' argument to the debugstablesort command Let start experimenting with other way to do stable sorting.

stablesort: rename function to stablesort_branchpoint We are about to test different approach to stable sorting. We clarify that the existing method is sorting from branch points.

stablerange: update the filename to avoid cache confusion The schema validation seems to not work as well as intended, we update the file name to make sure there will be no confusion.

stablesort: extract in its own module We are going to introduce variants, cache and more complex logic, we move that in its own repository beforehand.

compat: in depth cache, only use cachevfs when available We support older version without the new vfs.