dirstate-v2: Drop cached read_dir results after .hgignore changes Soon we’ll want the status algorithm to be able to skip `std::fs::read_dir` in more cases, notabling when listing unknown files but not ignored files. When ignore patterns change (which we detect by their hash, added to the dirstate-v2 format in a previous changeset), a formerly-ignored file could become unknown without changing its parent directory’s modification time. Therefore we remove any directory mtime from the dirstate, effictively invalidating the existing caches. Differential Revision: https://phab.mercurial-scm.org/D10907

censor: split the core of the logic into its own function We now have a "generic" rewrite function (only able to do censoring for now) and a thin wrapper that implement the `censor` API with it. We are now ready to start incorporating strip specific changes. Differential Revision: https://phab.mercurial-scm.org/D10904

censor: migrate the logic to a set of `censor_revs` Instead of considering a special unique censored revision within the code, we consider a set of revision (currently always of size 1). This make the main code less censor-centric and prepare for the usage of a similar approach for stripping changesets. Differential Revision: https://phab.mercurial-scm.org/D10903