rust: Remove DirstateMap::file_fold_map This was a HashMap constructed on demand and then cached in the DirstateMap struct to avoid reconstructing at the next access. However the only use is in Python bindings converting it to a PyDict. That method in turn is wrapped in a @cachedproperty in Python code. This was two redudant layers of caching. This changeset removes the Rust-level one to keep the Python dict cache, and have bindings create a PyDict by iterating. Differential Revision: https://phab.mercurial-scm.org/D10493

dirstate-tree: Add "non normal" and "from other parent" sets Unlike the other DirstateMap implementation, these sets are not materialized separately in memory. Instead we traverse the main tree. Differential Revision: https://phab.mercurial-scm.org/D10492

dirstate-tree: Add add_file, remove_file, and drop_file Again, various counters need to be kept up to date. Differential Revision: https://phab.mercurial-scm.org/D10491

dirstate-tree: Add has_dir and has_tracked_dir A node without a `DirstateMap` entry represents a directory. Only some values of `EntryState` represent tracked files. A directory is considered "tracked" if it contains any descendant file that is tracked. To avoid a sub-tree traversal in `has_tracked_dir` we add a counter for this. A boolean flag would become insufficent when we implement remove_file and drop_file. `add_file_node` is more general than needed here, in anticipation of adding the `add_file` and `remove_file` methods. Differential Revision: https://phab.mercurial-scm.org/D10490

dirstate-tree: Add clear_ambiguous_times in the new DirstateMap Also drive-by refactor it in the other DirstateMap Differential Revision: https://phab.mercurial-scm.org/D10489

dirstate-tree: Add copy_map_insert and copy_map_remove Differential Revision: https://phab.mercurial-scm.org/D10488

dirstate-tree: Maintain a counter of DirstateEntry’s and copy sources This allows implementing __len__ for DirstateMap and CopyMap efficiently, without traversing the tree. Differential Revision: https://phab.mercurial-scm.org/D10487

dirstate-tree: Serialize to disk The existing `pack_dirstate` function relies on implementation details of `DirstateMap`, so extract some parts of it as separate functions for us in the tree-based `DirstateMap`. The `bytes-cast` crate is updated to a version that has an `as_bytes` method, not just `from_bytes`: https://docs.rs/bytes-cast/0.2.0/bytes_cast/trait.BytesCast.html#method.as_bytes Drive-by refactor `clear_ambiguous_times` which does part of the same thing. Differential Revision: https://phab.mercurial-scm.org/D10486

rust: Add a Timestamp struct instead of abusing Duration `SystemTime` would be the standard library type semantically appropriate instead of `Duration`. But since the value is coming from Python as a plain integer and used in dirstate packing code as an integer, let’s make a type that contains a single integer instead of using one with sub-second precision. Differential Revision: https://phab.mercurial-scm.org/D10485

dirstate-tree: Add tree traversal/iteration Like Python’s, Rust’s iterators are "external" in that they are driven by a caller who calls a `next` method. This is as opposed to "internal" iterators who drive themselves and call a callback for each item. Writing an internal iterator traversing a tree is easy with recursion, but internal iterators cannot rely on the call stack in that way, they must save in an explicit object all state that they need to be preserved across two `next` calls. This algorithm uses a `Vec` as a stack that contains what would be local variables on the call stack if we could use recursion. Differential Revision: https://phab.mercurial-scm.org/D10370

dirstate-tree: Add map `get` and `contains_key` methods Differential Revision: https://phab.mercurial-scm.org/D10369

dirstate-tree: Add parsing only dirstate parents from disk Differential Revision: https://phab.mercurial-scm.org/D10368

dirstate-tree: Implement DirstateMap::read This reads the on-disk dirstate in its current format (a flat sequence of entries) and creates a tree in memory. Differential Revision: https://phab.mercurial-scm.org/D10367

dirstate-tree: Add `WithBasename` wrapper for `HgPath` In the tree-shaped dirstate we want to have nodes representing files or directories, where directory nodes contain a map associating "base" names to child nodes for child files and directories. Many dirstate operations expect a full path from the repository root, but re-concatenating string from nested map keys all the time might be expensive. Instead, `WithBasename` stores a full path for these operations but behaves as its base name (last path component) for equality and comparison. Additionally `inclusive_ancestors` provides the successive map keys that are needed when inserting a new dirstate node at a given full path. Differential Revision: https://phab.mercurial-scm.org/D10365

dirstate-tree: Empty shell for a second Rust DirstateMap implementation For background see description of the previous changeset "Make Rust DirstateMap bindings go through a trait object". Add an empty shell for a opt-in second Rust implementation of the `DirstateMap` type and the `status` function. For now all methods panic. This can be seen in "action" with: ./hg status --config experimental.dirstate-tree.in-memory=1 Differential Revision: https://phab.mercurial-scm.org/D10364