dirstate: introduce a symbolic constant for the FROM_P2 marker This is going to be clearer and easier to track than -2. Ultimately I would like to get ride of this special value everywhere but in the lower level, however we need to clarify the API first. This changeset is part of such clarification. Differential Revision: https://phab.mercurial-scm.org/D10926

dirstate: split a not-so-one-liner This is shorter and simpler to read. Differential Revision: https://phab.mercurial-scm.org/D10925

dirstate: split a not-so-one-liner This is simpler to read. Differential Revision: https://phab.mercurial-scm.org/D10924

dirstate: split a not-so-one-liner This is shorter and simpler to read. Differential Revision: https://phab.mercurial-scm.org/D10923

dirstate-tree: Keep a counter of descendant nodes that have an entry … and change the `DirstateMap::has_dir` method to be based on this counter being non-zero instead of the mere presence of a node. A node with zero descendent with an entry currently should be removed from the tree, but soon we’ll make the dirstate track additional nodes. (Specifically, for non-ignored directories in order to keep track of their mtime and optimize status by doing fewer `read_dir` calls.) Differential Revision: https://phab.mercurial-scm.org/D10922

dirstate: Removed unused instances of `DirsMultiset` … in Rust-backed dirstatemap. The Python class `dirstatemap` had cached properties `_dirs` and `_alldirs` that were not used for `hastrackeddir` and `hasdir` since they were redundant with corresponding fields for the Rust `DirstateMap` struct. `dirfoldmap` is modified to reuse instead the directory iterator introduced in 3b9914b28133c0918186b6e8b9e4f1916e21338d. Differential Revision: https://phab.mercurial-scm.org/D10921

dirstate-v2: Use 32-bit integers instead of 64-bit for offsets This saves 12 bytes per node. (Nodes representing files or directories.) These are offsets to other parts of the file. This would only be a limitation for a `.hg/dirstate` file larger than 4 GiB, which would only happen for a repository with dozens of millions of files and directories. Differential Revision: https://phab.mercurial-scm.org/D10920

status: Extend read_dir caching to directories with ignored files See code comments Differential Revision: https://phab.mercurial-scm.org/D10909

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