dirstate: move the copymap drop inside dropfile Since the copymap is part of the dirstatemap it make more sense for the dirstatemap to manage it directly. This is part of a generic effort to move unified logic at lower level and to clean up higher level API. Differential Revision: https://phab.mercurial-scm.org/D11417

rust: Rename get_node methods to data_for_node, get_rev to data_for_rev These are respective methods of Changelog, Manifestlog, and Filelog; three Rust structs that that wrap a Revlog struct. This rename clarifies that node IDs or revision numbers are parameters, not return values. Also reword doc-comments in Manifestlog and Filelog to separate node IDs and revision numbers that are local to a given (non-changelog) revlog from those of a changeset. Differential Revision: https://phab.mercurial-scm.org/D11416

rust: Rename the `Revlog::get_node_rev` method to `rev_from_node` This better describes the input and outputs of this method. Also rewrite the doc-comment, which seemed to have been left from copy-paste of another method. Differential Revision: https://phab.mercurial-scm.org/D11415

rust: Make private the `index` field of the `Revlog` struct To replace the previous use of this field from another module, add a `node_from_rev` method. This is the same method that already existed on `Changelog`. Differential Revision: https://phab.mercurial-scm.org/D11414

dirstate-v2: Remove the `.d` suffix in data file names It could cause confusion since `.d` is already used for revlogs. This suffix is not necessary since there is already a `dirstate.` prefix. Differential Revision: https://phab.mercurial-scm.org/D11413

rhg: Don’t compare ambiguous files one byte at a time Even though the use of `BufReader` reduces the number of syscalls to read the file from disk, `.bytes()` yields a separate `Result` for every byte. Creating those results and dispatching on them is most likely costly. Instead, this commit opts for simplicity by reading the entire file into memory and comparing a single pair of byte strings. Note that memory already needs to contain the entire previous contents of the file, as read from the filelog. So with an extremely large file this doubles memory use but does not make it grow by orders of magnitude. At first I wrote code that still avoids reading the entire file into memory and compares one buffer at a time with `BufReader`. Find this code below for posterity. However its correctness is subtle. I ended up preferring the simplicity of the obviously-correct single comparison. ```rust let mut reader = BufReader::new(fobj); let mut expected = &contents_in_p1[..]; loop { let buf = reader.fill_buf().when_reading_file(&fs_path)?; if buf.is_empty() { // Found EOF return Ok(expected.is_empty()); } else if let Some(rest) = expected.drop_prefix(buf) { // What we read so far matches the expected content, continue reading let buf_len = buf.len(); reader.consume(buf_len); expected = rest } else { // Found different content return Ok(false); } } ``` Differential Revision: https://phab.mercurial-scm.org/D11412