rust-dirs-multiset: add `DirsChildrenMultiset`

In a future patch, this structure will be needed to store information needed by
the (also upcoming) `IgnoreMatcher`.

Differential Revision: https://phab.mercurial-scm.org/D7869

rust/hg-core/src/dirstate/dirs_multiset.rs

@@ -1,346 +1,411 b''
 // dirs_multiset.rs
 //
 // Copyright 2019 Raphaël Gomès <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 //! A multiset of directory names.
 //!
 //! Used to counts the references to directories in a manifest or dirstate.
-use crate::utils::hg_path::{HgPath, HgPathBuf};
 use crate::{
-    dirstate::EntryState, utils::files, DirstateEntry, DirstateMapError,
-    FastHashMap,
+    dirstate::EntryState,
+    utils::{
+        files,
+        hg_path::{HgPath, HgPathBuf},
+    },
+    DirstateEntry, DirstateMapError, FastHashMap,
 };
-use std::collections::hash_map::{self, Entry};
+use std::collections::{hash_map, hash_map::Entry, HashMap, HashSet};
 
 // could be encapsulated if we care API stability more seriously
 pub type DirsMultisetIter<'a> = hash_map::Keys<'a, HgPathBuf, u32>;
 
 #[derive(PartialEq, Debug)]
 pub struct DirsMultiset {
     inner: FastHashMap<HgPathBuf, u32>,
 }
 
 impl DirsMultiset {
     /// Initializes the multiset from a dirstate.
     ///
     /// If `skip_state` is provided, skips dirstate entries with equal state.
     pub fn from_dirstate(
         dirstate: &FastHashMap<HgPathBuf, DirstateEntry>,
         skip_state: Option<EntryState>,
     ) -> Result<Self, DirstateMapError> {
         let mut multiset = DirsMultiset {
             inner: FastHashMap::default(),
         };
 
         for (filename, DirstateEntry { state, .. }) in dirstate {
             // This `if` is optimized out of the loop
             if let Some(skip) = skip_state {
                 if skip != *state {
                     multiset.add_path(filename)?;
                 }
             } else {
                 multiset.add_path(filename)?;
             }
         }
 
         Ok(multiset)
     }
 
     /// Initializes the multiset from a manifest.
     pub fn from_manifest(
         manifest: &[impl AsRef<HgPath>],
     ) -> Result<Self, DirstateMapError> {
         let mut multiset = DirsMultiset {
             inner: FastHashMap::default(),
         };
 
         for filename in manifest {
             multiset.add_path(filename.as_ref())?;
         }
 
         Ok(multiset)
     }
 
     /// Increases the count of deepest directory contained in the path.
     ///
     /// If the directory is not yet in the map, adds its parents.
     pub fn add_path(
         &mut self,
         path: impl AsRef<HgPath>,
     ) -> Result<(), DirstateMapError> {
         for subpath in files::find_dirs(path.as_ref()) {
             if subpath.as_bytes().last() == Some(&b'/') {
                 // TODO Remove this once PathAuditor is certified
                 // as the only entrypoint for path data
                 return Err(DirstateMapError::ConsecutiveSlashes);
             }
             if let Some(val) = self.inner.get_mut(subpath) {
                 *val += 1;
                 break;
             }
             self.inner.insert(subpath.to_owned(), 1);
         }
         Ok(())
     }
 
     /// Decreases the count of deepest directory contained in the path.
     ///
     /// If it is the only reference, decreases all parents until one is
     /// removed.
     /// If the directory is not in the map, something horrible has happened.
     pub fn delete_path(
         &mut self,
         path: impl AsRef<HgPath>,
     ) -> Result<(), DirstateMapError> {
         for subpath in files::find_dirs(path.as_ref()) {
             match self.inner.entry(subpath.to_owned()) {
                 Entry::Occupied(mut entry) => {
                     let val = entry.get().clone();
                     if val > 1 {
                         entry.insert(val - 1);
                         break;
                     }
                     entry.remove();
                 }
                 Entry::Vacant(_) => {
                     return Err(DirstateMapError::PathNotFound(
                         path.as_ref().to_owned(),
                     ))
                 }
             };
         }
 
         Ok(())
     }
 
     pub fn contains(&self, key: impl AsRef<HgPath>) -> bool {
         self.inner.contains_key(key.as_ref())
     }
 
     pub fn iter(&self) -> DirsMultisetIter {
         self.inner.keys()
     }
 
     pub fn len(&self) -> usize {
         self.inner.len()
     }
 }
 
+/// This is basically a reimplementation of `DirsMultiset` that stores the
+/// children instead of just a count of them, plus a small optional
+/// optimization to avoid some directories we don't need.
+#[derive(PartialEq, Debug)]
+pub struct DirsChildrenMultiset<'a> {
+    inner: FastHashMap<&'a HgPath, HashSet<&'a HgPath>>,
+    only_include: Option<HashSet<&'a HgPath>>,
+}
+
+impl<'a> DirsChildrenMultiset<'a> {
+    pub fn new(
+        paths: impl Iterator<Item = &'a HgPathBuf>,
+        only_include: Option<&'a HashSet<impl AsRef<HgPath> + 'a>>,
+    ) -> Self {
+        let mut new = Self {
+            inner: HashMap::default(),
+            only_include: only_include
+                .map(|s| s.iter().map(|p| p.as_ref()).collect()),
+        };
+
+        for path in paths {
+            new.add_path(path)
+        }
+
+        new
+    }
+    fn add_path(&mut self, path: &'a (impl AsRef<HgPath> + 'a)) {
+        if path.as_ref().is_empty() {
+            return;
+        }
+        for (directory, basename) in files::find_dirs_with_base(path.as_ref())
+        {
+            if !self.is_dir_included(directory) {
+                continue;
+            }
+            self.inner
+                .entry(directory)
+                .and_modify(|e| {
+                    e.insert(basename);
+                })
+                .or_insert_with(|| {
+                    let mut set = HashSet::new();
+                    set.insert(basename);
+                    set
+                });
+        }
+    }
+    fn is_dir_included(&self, dir: impl AsRef<HgPath>) -> bool {
+        match &self.only_include {
+            None => false,
+            Some(i) => i.contains(dir.as_ref()),
+        }
+    }
+
+    pub fn get(
+        &self,
+        path: impl AsRef<HgPath>,
+    ) -> Option<&HashSet<&'a HgPath>> {
+        self.inner.get(path.as_ref())
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
     #[test]
     fn test_delete_path_path_not_found() {
         let manifest: Vec<HgPathBuf> = vec![];
         let mut map = DirsMultiset::from_manifest(&manifest).unwrap();
         let path = HgPathBuf::from_bytes(b"doesnotexist/");
         assert_eq!(
             Err(DirstateMapError::PathNotFound(path.to_owned())),
             map.delete_path(&path)
         );
     }
 
     #[test]
     fn test_delete_path_empty_path() {
         let mut map =
             DirsMultiset::from_manifest(&vec![HgPathBuf::new()]).unwrap();
         let path = HgPath::new(b"");
         assert_eq!(Ok(()), map.delete_path(path));
         assert_eq!(
             Err(DirstateMapError::PathNotFound(path.to_owned())),
             map.delete_path(path)
         );
     }
 
     #[test]
     fn test_delete_path_successful() {
         let mut map = DirsMultiset {
             inner: [("", 5), ("a", 3), ("a/b", 2), ("a/c", 1)]
                 .iter()
                 .map(|(k, v)| (HgPathBuf::from_bytes(k.as_bytes()), *v))
                 .collect(),
         };
 
         assert_eq!(Ok(()), map.delete_path(HgPath::new(b"a/b/")));
         eprintln!("{:?}", map);
         assert_eq!(Ok(()), map.delete_path(HgPath::new(b"a/b/")));
         eprintln!("{:?}", map);
         assert_eq!(
             Err(DirstateMapError::PathNotFound(HgPathBuf::from_bytes(
                 b"a/b/"
             ))),
             map.delete_path(HgPath::new(b"a/b/"))
         );
 
         assert_eq!(2, *map.inner.get(HgPath::new(b"a")).unwrap());
         assert_eq!(1, *map.inner.get(HgPath::new(b"a/c")).unwrap());
         eprintln!("{:?}", map);
         assert_eq!(Ok(()), map.delete_path(HgPath::new(b"a/")));
         eprintln!("{:?}", map);
 
         assert_eq!(Ok(()), map.delete_path(HgPath::new(b"a/c/")));
         assert_eq!(
             Err(DirstateMapError::PathNotFound(HgPathBuf::from_bytes(
                 b"a/c/"
             ))),
             map.delete_path(HgPath::new(b"a/c/"))
         );
     }
 
     #[test]
     fn test_add_path_empty_path() {
         let manifest: Vec<HgPathBuf> = vec![];
         let mut map = DirsMultiset::from_manifest(&manifest).unwrap();
         let path = HgPath::new(b"");
         map.add_path(path).unwrap();
 
         assert_eq!(1, map.len());
     }
 
     #[test]
     fn test_add_path_successful() {
         let manifest: Vec<HgPathBuf> = vec![];
         let mut map = DirsMultiset::from_manifest(&manifest).unwrap();
 
         map.add_path(HgPath::new(b"a/")).unwrap();
         assert_eq!(1, *map.inner.get(HgPath::new(b"a")).unwrap());
         assert_eq!(1, *map.inner.get(HgPath::new(b"")).unwrap());
         assert_eq!(2, map.len());
 
         // Non directory should be ignored
         map.add_path(HgPath::new(b"a")).unwrap();
         assert_eq!(1, *map.inner.get(HgPath::new(b"a")).unwrap());
         assert_eq!(2, map.len());
 
         // Non directory will still add its base
         map.add_path(HgPath::new(b"a/b")).unwrap();
         assert_eq!(2, *map.inner.get(HgPath::new(b"a")).unwrap());
         assert_eq!(2, map.len());
 
         // Duplicate path works
         map.add_path(HgPath::new(b"a/")).unwrap();
         assert_eq!(3, *map.inner.get(HgPath::new(b"a")).unwrap());
 
         // Nested dir adds to its base
         map.add_path(HgPath::new(b"a/b/")).unwrap();
         assert_eq!(4, *map.inner.get(HgPath::new(b"a")).unwrap());
         assert_eq!(1, *map.inner.get(HgPath::new(b"a/b")).unwrap());
 
         // but not its base's base, because it already existed
         map.add_path(HgPath::new(b"a/b/c/")).unwrap();
         assert_eq!(4, *map.inner.get(HgPath::new(b"a")).unwrap());
         assert_eq!(2, *map.inner.get(HgPath::new(b"a/b")).unwrap());
 
         map.add_path(HgPath::new(b"a/c/")).unwrap();
         assert_eq!(1, *map.inner.get(HgPath::new(b"a/c")).unwrap());
 
         let expected = DirsMultiset {
             inner: [("", 2), ("a", 5), ("a/b", 2), ("a/b/c", 1), ("a/c", 1)]
                 .iter()
                 .map(|(k, v)| (HgPathBuf::from_bytes(k.as_bytes()), *v))
                 .collect(),
         };
         assert_eq!(map, expected);
     }
 
     #[test]
     fn test_dirsmultiset_new_empty() {
         let manifest: Vec<HgPathBuf> = vec![];
         let new = DirsMultiset::from_manifest(&manifest).unwrap();
         let expected = DirsMultiset {
             inner: FastHashMap::default(),
         };
         assert_eq!(expected, new);
 
         let new = DirsMultiset::from_dirstate(&FastHashMap::default(), None)
             .unwrap();
         let expected = DirsMultiset {
             inner: FastHashMap::default(),
         };
         assert_eq!(expected, new);
     }
 
     #[test]
     fn test_dirsmultiset_new_no_skip() {
         let input_vec: Vec<HgPathBuf> = ["a/", "b/", "a/c", "a/d/"]
             .iter()
             .map(|e| HgPathBuf::from_bytes(e.as_bytes()))
             .collect();
         let expected_inner = [("", 2), ("a", 3), ("b", 1), ("a/d", 1)]
             .iter()
             .map(|(k, v)| (HgPathBuf::from_bytes(k.as_bytes()), *v))
             .collect();
 
         let new = DirsMultiset::from_manifest(&input_vec).unwrap();
         let expected = DirsMultiset {
             inner: expected_inner,
         };
         assert_eq!(expected, new);
 
         let input_map = ["a/", "b/", "a/c", "a/d/"]
             .iter()
             .map(|f| {
                 (
                     HgPathBuf::from_bytes(f.as_bytes()),
                     DirstateEntry {
                         state: EntryState::Normal,
                         mode: 0,
                         mtime: 0,
                         size: 0,
                     },
                 )
             })
             .collect();
         let expected_inner = [("", 2), ("a", 3), ("b", 1), ("a/d", 1)]
             .iter()
             .map(|(k, v)| (HgPathBuf::from_bytes(k.as_bytes()), *v))
             .collect();
 
         let new = DirsMultiset::from_dirstate(&input_map, None).unwrap();
         let expected = DirsMultiset {
             inner: expected_inner,
         };
         assert_eq!(expected, new);
     }
 
     #[test]
     fn test_dirsmultiset_new_skip() {
         let input_map = [
             ("a/", EntryState::Normal),
             ("a/b/", EntryState::Normal),
             ("a/c", EntryState::Removed),
             ("a/d/", EntryState::Merged),
         ]
         .iter()
         .map(|(f, state)| {
             (
                 HgPathBuf::from_bytes(f.as_bytes()),
                 DirstateEntry {
                     state: *state,
                     mode: 0,
                     mtime: 0,
                     size: 0,
                 },
             )
         })
         .collect();
 
         // "a" incremented with "a/c" and "a/d/"
         let expected_inner = [("", 1), ("a", 2), ("a/d", 1)]
             .iter()
             .map(|(k, v)| (HgPathBuf::from_bytes(k.as_bytes()), *v))
             .collect();
 
         let new =
             DirsMultiset::from_dirstate(&input_map, Some(EntryState::Normal))
                 .unwrap();
         let expected = DirsMultiset {
             inner: expected_inner,
         };
         assert_eq!(expected, new);
     }
 }

rust/hg-core/src/utils/files.rs

@@ -1,173 +1,238 b''
 // files.rs
 //
 // Copyright 2019
 // Raphaël Gomès <[e-mail]>,
 // Yuya Nishihara <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 //! Functions for fiddling with files.
 
 use crate::utils::hg_path::{HgPath, HgPathBuf};
-use std::iter::FusedIterator;
 
 use crate::utils::replace_slice;
 use lazy_static::lazy_static;
 use std::fs::Metadata;
+use std::iter::FusedIterator;
 use std::path::Path;
 
 pub fn get_path_from_bytes(bytes: &[u8]) -> &Path {
     let os_str;
     #[cfg(unix)]
     {
         use std::os::unix::ffi::OsStrExt;
         os_str = std::ffi::OsStr::from_bytes(bytes);
     }
     // TODO Handle other platforms
     // TODO: convert from WTF8 to Windows MBCS (ANSI encoding).
     // Perhaps, the return type would have to be Result<PathBuf>.
 
     Path::new(os_str)
 }
 
 // TODO: need to convert from WTF8 to MBCS bytes on Windows.
 // that's why Vec<u8> is returned.
 #[cfg(unix)]
 pub fn get_bytes_from_path(path: impl AsRef<Path>) -> Vec<u8> {
     use std::os::unix::ffi::OsStrExt;
     path.as_ref().as_os_str().as_bytes().to_vec()
 }
 
 /// An iterator over repository path yielding itself and its ancestors.
 #[derive(Copy, Clone, Debug)]
 pub struct Ancestors<'a> {
     next: Option<&'a HgPath>,
 }
 
 impl<'a> Iterator for Ancestors<'a> {
     type Item = &'a HgPath;
 
     fn next(&mut self) -> Option<Self::Item> {
         let next = self.next;
         self.next = match self.next {
             Some(s) if s.is_empty() => None,
             Some(s) => {
                 let p = s.bytes().rposition(|c| *c == b'/').unwrap_or(0);
                 Some(HgPath::new(&s.as_bytes()[..p]))
             }
             None => None,
         };
         next
     }
 }
 
 impl<'a> FusedIterator for Ancestors<'a> {}
 
+/// An iterator over repository path yielding itself and its ancestors.
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct AncestorsWithBase<'a> {
+    next: Option<(&'a HgPath, &'a HgPath)>,
+}
+
+impl<'a> Iterator for AncestorsWithBase<'a> {
+    type Item = (&'a HgPath, &'a HgPath);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let next = self.next;
+        self.next = match self.next {
+            Some((s, _)) if s.is_empty() => None,
+            Some((s, _)) => Some(s.split_filename()),
+            None => None,
+        };
+        next
+    }
+}
+
+impl<'a> FusedIterator for AncestorsWithBase<'a> {}
+
 /// Returns an iterator yielding ancestor directories of the given repository
 /// path.
 ///
 /// The path is separated by '/', and must not start with '/'.
 ///
 /// The path itself isn't included unless it is b"" (meaning the root
 /// directory.)
 pub fn find_dirs<'a>(path: &'a HgPath) -> Ancestors<'a> {
     let mut dirs = Ancestors { next: Some(path) };
     if !path.is_empty() {
         dirs.next(); // skip itself
     }
     dirs
 }
 
+/// Returns an iterator yielding ancestor directories of the given repository
+/// path.
+///
+/// The path is separated by '/', and must not start with '/'.
+///
+/// The path itself isn't included unless it is b"" (meaning the root
+/// directory.)
+pub(crate) fn find_dirs_with_base<'a>(
+    path: &'a HgPath,
+) -> AncestorsWithBase<'a> {
+    let mut dirs = AncestorsWithBase {
+        next: Some((path, HgPath::new(b""))),
+    };
+    if !path.is_empty() {
+        dirs.next(); // skip itself
+    }
+    dirs
+}
+
 /// TODO more than ASCII?
 pub fn normalize_case(path: &HgPath) -> HgPathBuf {
     #[cfg(windows)] // NTFS compares via upper()
     return path.to_ascii_uppercase();
     #[cfg(unix)]
     path.to_ascii_lowercase()
 }
 
 lazy_static! {
     static ref IGNORED_CHARS: Vec<Vec<u8>> = {
         [
             0x200c, 0x200d, 0x200e, 0x200f, 0x202a, 0x202b, 0x202c, 0x202d,
             0x202e, 0x206a, 0x206b, 0x206c, 0x206d, 0x206e, 0x206f, 0xfeff,
         ]
         .iter()
         .map(|code| {
             std::char::from_u32(*code)
                 .unwrap()
                 .encode_utf8(&mut [0; 3])
                 .bytes()
                 .collect()
         })
         .collect()
     };
 }
 
 fn hfs_ignore_clean(bytes: &[u8]) -> Vec<u8> {
     let mut buf = bytes.to_owned();
     let needs_escaping = bytes.iter().any(|b| *b == b'\xe2' || *b == b'\xef');
     if needs_escaping {
         for forbidden in IGNORED_CHARS.iter() {
             replace_slice(&mut buf, forbidden, &[])
         }
         buf
     } else {
         buf
     }
 }
 
 pub fn lower_clean(bytes: &[u8]) -> Vec<u8> {
     hfs_ignore_clean(&bytes.to_ascii_lowercase())
 }
 
 #[derive(Eq, PartialEq, Ord, PartialOrd, Copy, Clone)]
 pub struct HgMetadata {
     pub st_dev: u64,
     pub st_mode: u32,
     pub st_nlink: u64,
     pub st_size: u64,
     pub st_mtime: i64,
     pub st_ctime: i64,
 }
 
 // TODO support other plaforms
 #[cfg(unix)]
 impl HgMetadata {
     pub fn from_metadata(metadata: Metadata) -> Self {
         use std::os::unix::fs::MetadataExt;
         Self {
             st_dev: metadata.dev(),
             st_mode: metadata.mode(),
             st_nlink: metadata.nlink(),
             st_size: metadata.size(),
             st_mtime: metadata.mtime(),
             st_ctime: metadata.ctime(),
         }
     }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
 
     #[test]
     fn find_dirs_some() {
         let mut dirs = super::find_dirs(HgPath::new(b"foo/bar/baz"));
         assert_eq!(dirs.next(), Some(HgPath::new(b"foo/bar")));
         assert_eq!(dirs.next(), Some(HgPath::new(b"foo")));
         assert_eq!(dirs.next(), Some(HgPath::new(b"")));
         assert_eq!(dirs.next(), None);
         assert_eq!(dirs.next(), None);
     }
 
     #[test]
     fn find_dirs_empty() {
         // looks weird, but mercurial.pathutil.finddirs(b"") yields b""
         let mut dirs = super::find_dirs(HgPath::new(b""));
         assert_eq!(dirs.next(), Some(HgPath::new(b"")));
         assert_eq!(dirs.next(), None);
         assert_eq!(dirs.next(), None);
     }
+
+    #[test]
+    fn test_find_dirs_with_base_some() {
+        let mut dirs = super::find_dirs_with_base(HgPath::new(b"foo/bar/baz"));
+        assert_eq!(
+            dirs.next(),
+            Some((HgPath::new(b"foo/bar"), HgPath::new(b"baz")))
+        );
+        assert_eq!(
+            dirs.next(),
+            Some((HgPath::new(b"foo"), HgPath::new(b"bar")))
+        );
+        assert_eq!(dirs.next(), Some((HgPath::new(b""), HgPath::new(b"foo"))));
+        assert_eq!(dirs.next(), None);
+        assert_eq!(dirs.next(), None);
+    }
+
+    #[test]
+    fn test_find_dirs_with_base_empty() {
+        let mut dirs = super::find_dirs_with_base(HgPath::new(b""));
+        assert_eq!(dirs.next(), Some((HgPath::new(b""), HgPath::new(b""))));
+        assert_eq!(dirs.next(), None);
+        assert_eq!(dirs.next(), None);
+    }
 }

rust/hg-core/src/utils/hg_path.rs

@@ -1,745 +1,768 b''
 // hg_path.rs
 //
 // Copyright 2019 Raphaël Gomès <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 use std::borrow::Borrow;
 use std::ffi::{OsStr, OsString};
 use std::fmt;
 use std::ops::Deref;
 use std::path::{Path, PathBuf};
 
 #[derive(Debug, Eq, PartialEq)]
 pub enum HgPathError {
     /// Bytes from the invalid `HgPath`
     LeadingSlash(Vec<u8>),
     ConsecutiveSlashes {
         bytes: Vec<u8>,
         second_slash_index: usize,
     },
     ContainsNullByte {
         bytes: Vec<u8>,
         null_byte_index: usize,
     },
     /// Bytes
     DecodeError(Vec<u8>),
     /// The rest come from audit errors
     EndsWithSlash(HgPathBuf),
     ContainsIllegalComponent(HgPathBuf),
     /// Path is inside the `.hg` folder
     InsideDotHg(HgPathBuf),
     IsInsideNestedRepo {
         path: HgPathBuf,
         nested_repo: HgPathBuf,
     },
     TraversesSymbolicLink {
         path: HgPathBuf,
         symlink: HgPathBuf,
     },
     NotFsCompliant(HgPathBuf),
     /// `path` is the smallest invalid path
     NotUnderRoot {
         path: PathBuf,
         root: PathBuf,
     },
 }
 
 impl ToString for HgPathError {
     fn to_string(&self) -> String {
         match self {
             HgPathError::LeadingSlash(bytes) => {
                 format!("Invalid HgPath '{:?}': has a leading slash.", bytes)
             }
             HgPathError::ConsecutiveSlashes {
                 bytes,
                 second_slash_index: pos,
             } => format!(
                 "Invalid HgPath '{:?}': consecutive slashes at pos {}.",
                 bytes, pos
             ),
             HgPathError::ContainsNullByte {
                 bytes,
                 null_byte_index: pos,
             } => format!(
                 "Invalid HgPath '{:?}': contains null byte at pos {}.",
                 bytes, pos
             ),
             HgPathError::DecodeError(bytes) => {
                 format!("Invalid HgPath '{:?}': could not be decoded.", bytes)
             }
             HgPathError::EndsWithSlash(path) => {
                 format!("Audit failed for '{}': ends with a slash.", path)
             }
             HgPathError::ContainsIllegalComponent(path) => format!(
                 "Audit failed for '{}': contains an illegal component.",
                 path
             ),
             HgPathError::InsideDotHg(path) => format!(
                 "Audit failed for '{}': is inside the '.hg' folder.",
                 path
             ),
             HgPathError::IsInsideNestedRepo {
                 path,
                 nested_repo: nested,
             } => format!(
                 "Audit failed for '{}': is inside a nested repository '{}'.",
                 path, nested
             ),
             HgPathError::TraversesSymbolicLink { path, symlink } => format!(
                 "Audit failed for '{}': traverses symbolic link '{}'.",
                 path, symlink
             ),
             HgPathError::NotFsCompliant(path) => format!(
                 "Audit failed for '{}': cannot be turned into a \
                  filesystem path.",
                 path
             ),
             HgPathError::NotUnderRoot { path, root } => format!(
                 "Audit failed for '{}': not under root {}.",
                 path.display(),
                 root.display()
             ),
         }
     }
 }
 
 impl From<HgPathError> for std::io::Error {
     fn from(e: HgPathError) -> Self {
         std::io::Error::new(std::io::ErrorKind::InvalidData, e.to_string())
     }
 }
 
 /// This is a repository-relative path (or canonical path):
 ///     - no null characters
 ///     - `/` separates directories
 ///     - no consecutive slashes
 ///     - no leading slash,
 ///     - no `.` nor `..` of special meaning
 ///     - stored in repository and shared across platforms
 ///
 /// Note: there is no guarantee of any `HgPath` being well-formed at any point
 /// in its lifetime for performance reasons and to ease ergonomics. It is
 /// however checked using the `check_state` method before any file-system
 /// operation.
 ///
 /// This allows us to be encoding-transparent as much as possible, until really
 /// needed; `HgPath` can be transformed into a platform-specific path (`OsStr`
 /// or `Path`) whenever more complex operations are needed:
 /// On Unix, it's just byte-to-byte conversion. On Windows, it has to be
 /// decoded from MBCS to WTF-8. If WindowsUTF8Plan is implemented, the source
 /// character encoding will be determined on a per-repository basis.
 //
 // FIXME: (adapted from a comment in the stdlib)
 // `HgPath::new()` current implementation relies on `Slice` being
 // layout-compatible with `[u8]`.
 // When attribute privacy is implemented, `Slice` should be annotated as
 // `#[repr(transparent)]`.
 // Anyway, `Slice` representation and layout are considered implementation
 // detail, are not documented and must not be relied upon.
 #[derive(Eq, Ord, PartialEq, PartialOrd, Hash)]
 pub struct HgPath {
     inner: [u8],
 }
 
 impl HgPath {
     pub fn new<S: AsRef<[u8]> + ?Sized>(s: &S) -> &Self {
         unsafe { &*(s.as_ref() as *const [u8] as *const Self) }
     }
     pub fn is_empty(&self) -> bool {
         self.inner.is_empty()
     }
     pub fn len(&self) -> usize {
         self.inner.len()
     }
     fn to_hg_path_buf(&self) -> HgPathBuf {
         HgPathBuf {
             inner: self.inner.to_owned(),
         }
     }
     pub fn bytes(&self) -> std::slice::Iter<u8> {
         self.inner.iter()
     }
     pub fn to_ascii_uppercase(&self) -> HgPathBuf {
         HgPathBuf::from(self.inner.to_ascii_uppercase())
     }
     pub fn to_ascii_lowercase(&self) -> HgPathBuf {
         HgPathBuf::from(self.inner.to_ascii_lowercase())
     }
     pub fn as_bytes(&self) -> &[u8] {
         &self.inner
     }
     pub fn contains(&self, other: u8) -> bool {
         self.inner.contains(&other)
     }
     pub fn starts_with(&self, needle: impl AsRef<Self>) -> bool {
         self.inner.starts_with(needle.as_ref().as_bytes())
     }
     pub fn trim_trailing_slash(&self) -> &Self {
         Self::new(if self.inner.last() == Some(&b'/') {
             &self.inner[..self.inner.len() - 1]
         } else {
             &self.inner[..]
         })
     }
+    /// Returns a tuple of slices `(base, filename)` resulting from the split
+    /// at the rightmost `/`, if any.
+    ///
+    /// # Examples:
+    ///
+    /// ```
+    /// use hg::utils::hg_path::HgPath;
+    ///
+    /// let path = HgPath::new(b"cool/hg/path").split_filename();
+    /// assert_eq!(path, (HgPath::new(b"cool/hg"), HgPath::new(b"path")));
+    ///
+    /// let path = HgPath::new(b"pathwithoutsep").split_filename();
+    /// assert_eq!(path, (HgPath::new(b""), HgPath::new(b"pathwithoutsep")));
+    /// ```
+    pub fn split_filename(&self) -> (&Self, &Self) {
+        match &self.inner.iter().rposition(|c| *c == b'/') {
+            None => (HgPath::new(""), &self),
+            Some(size) => (
+                HgPath::new(&self.inner[..*size]),
+                HgPath::new(&self.inner[*size + 1..]),
+            ),
+        }
+    }
     pub fn join<T: ?Sized + AsRef<Self>>(&self, other: &T) -> HgPathBuf {
         let mut inner = self.inner.to_owned();
         if inner.len() != 0 && inner.last() != Some(&b'/') {
             inner.push(b'/');
         }
         inner.extend(other.as_ref().bytes());
         HgPathBuf::from_bytes(&inner)
     }
     pub fn parent(&self) -> &Self {
         let inner = self.as_bytes();
         HgPath::new(match inner.iter().rposition(|b| *b == b'/') {
             Some(pos) => &inner[..pos],
             None => &[],
         })
     }
     /// Given a base directory, returns the slice of `self` relative to the
     /// base directory. If `base` is not a directory (does not end with a
     /// `b'/'`), returns `None`.
     pub fn relative_to(&self, base: impl AsRef<Self>) -> Option<&Self> {
         let base = base.as_ref();
         if base.is_empty() {
             return Some(self);
         }
         let is_dir = base.as_bytes().ends_with(b"/");
         if is_dir && self.starts_with(base) {
             Some(Self::new(&self.inner[base.len()..]))
         } else {
             None
         }
     }
 
     #[cfg(windows)]
     /// Copied from the Python stdlib's `os.path.splitdrive` implementation.
     ///
     /// Split a pathname into drive/UNC sharepoint and relative path
     /// specifiers. Returns a 2-tuple (drive_or_unc, path); either part may
     /// be empty.
     ///
     /// If you assign
     ///  result = split_drive(p)
     /// It is always true that:
     ///  result[0] + result[1] == p
     ///
     /// If the path contained a drive letter, drive_or_unc will contain
     /// everything up to and including the colon.
     /// e.g. split_drive("c:/dir") returns ("c:", "/dir")
     ///
     /// If the path contained a UNC path, the drive_or_unc will contain the
     /// host name and share up to but not including the fourth directory
     /// separator character.
     /// e.g. split_drive("//host/computer/dir") returns ("//host/computer",
     /// "/dir")
     ///
     /// Paths cannot contain both a drive letter and a UNC path.
     pub fn split_drive<'a>(&self) -> (&HgPath, &HgPath) {
         let bytes = self.as_bytes();
         let is_sep = |b| std::path::is_separator(b as char);
 
         if self.len() < 2 {
             (HgPath::new(b""), &self)
         } else if is_sep(bytes[0])
             && is_sep(bytes[1])
             && (self.len() == 2 || !is_sep(bytes[2]))
         {
             // Is a UNC path:
             // vvvvvvvvvvvvvvvvvvvv drive letter or UNC path
             // \\machine\mountpoint\directory\etc\...
             //           directory ^^^^^^^^^^^^^^^
 
             let machine_end_index = bytes[2..].iter().position(|b| is_sep(*b));
             let mountpoint_start_index = if let Some(i) = machine_end_index {
                 i + 2
             } else {
                 return (HgPath::new(b""), &self);
             };
 
             match bytes[mountpoint_start_index + 1..]
                 .iter()
                 .position(|b| is_sep(*b))
             {
                 // A UNC path can't have two slashes in a row
                 // (after the initial two)
                 Some(0) => (HgPath::new(b""), &self),
                 Some(i) => {
                     let (a, b) =
                         bytes.split_at(mountpoint_start_index + 1 + i);
                     (HgPath::new(a), HgPath::new(b))
                 }
                 None => (&self, HgPath::new(b"")),
             }
         } else if bytes[1] == b':' {
             // Drive path c:\directory
             let (a, b) = bytes.split_at(2);
             (HgPath::new(a), HgPath::new(b))
         } else {
             (HgPath::new(b""), &self)
         }
     }
 
     #[cfg(unix)]
     /// Split a pathname into drive and path. On Posix, drive is always empty.
     pub fn split_drive(&self) -> (&HgPath, &HgPath) {
         (HgPath::new(b""), &self)
     }
 
     /// Checks for errors in the path, short-circuiting at the first one.
     /// This generates fine-grained errors useful for debugging.
     /// To simply check if the path is valid during tests, use `is_valid`.
     pub fn check_state(&self) -> Result<(), HgPathError> {
         if self.len() == 0 {
             return Ok(());
         }
         let bytes = self.as_bytes();
         let mut previous_byte = None;
 
         if bytes[0] == b'/' {
             return Err(HgPathError::LeadingSlash(bytes.to_vec()));
         }
         for (index, byte) in bytes.iter().enumerate() {
             match byte {
                 0 => {
                     return Err(HgPathError::ContainsNullByte {
                         bytes: bytes.to_vec(),
                         null_byte_index: index,
                     })
                 }
                 b'/' => {
                     if previous_byte.is_some() && previous_byte == Some(b'/') {
                         return Err(HgPathError::ConsecutiveSlashes {
                             bytes: bytes.to_vec(),
                             second_slash_index: index,
                         });
                     }
                 }
                 _ => (),
             };
             previous_byte = Some(*byte);
         }
         Ok(())
     }
 
     #[cfg(test)]
     /// Only usable during tests to force developers to handle invalid states
     fn is_valid(&self) -> bool {
         self.check_state().is_ok()
     }
 }
 
 impl fmt::Debug for HgPath {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "HgPath({:?})", String::from_utf8_lossy(&self.inner))
     }
 }
 
 impl fmt::Display for HgPath {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", String::from_utf8_lossy(&self.inner))
     }
 }
 
 #[derive(Eq, Ord, Clone, PartialEq, PartialOrd, Hash)]
 pub struct HgPathBuf {
     inner: Vec<u8>,
 }
 
 impl HgPathBuf {
     pub fn new() -> Self {
         Self { inner: Vec::new() }
     }
     pub fn push(&mut self, byte: u8) {
         self.inner.push(byte);
     }
     pub fn from_bytes(s: &[u8]) -> HgPathBuf {
         HgPath::new(s).to_owned()
     }
     pub fn into_vec(self) -> Vec<u8> {
         self.inner
     }
     pub fn as_ref(&self) -> &[u8] {
         self.inner.as_ref()
     }
 }
 
 impl fmt::Debug for HgPathBuf {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "HgPathBuf({:?})", String::from_utf8_lossy(&self.inner))
     }
 }
 
 impl fmt::Display for HgPathBuf {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", String::from_utf8_lossy(&self.inner))
     }
 }
 
 impl Deref for HgPathBuf {
     type Target = HgPath;
 
     #[inline]
     fn deref(&self) -> &HgPath {
         &HgPath::new(&self.inner)
     }
 }
 
 impl From<Vec<u8>> for HgPathBuf {
     fn from(vec: Vec<u8>) -> Self {
         Self { inner: vec }
     }
 }
 
 impl<T: ?Sized + AsRef<HgPath>> From<&T> for HgPathBuf {
     fn from(s: &T) -> HgPathBuf {
         s.as_ref().to_owned()
     }
 }
 
 impl Into<Vec<u8>> for HgPathBuf {
     fn into(self) -> Vec<u8> {
         self.inner
     }
 }
 
 impl Borrow<HgPath> for HgPathBuf {
     fn borrow(&self) -> &HgPath {
         &HgPath::new(self.as_bytes())
     }
 }
 
 impl ToOwned for HgPath {
     type Owned = HgPathBuf;
 
     fn to_owned(&self) -> HgPathBuf {
         self.to_hg_path_buf()
     }
 }
 
 impl AsRef<HgPath> for HgPath {
     fn as_ref(&self) -> &HgPath {
         self
     }
 }
 
 impl AsRef<HgPath> for HgPathBuf {
     fn as_ref(&self) -> &HgPath {
         self
     }
 }
 
 impl Extend<u8> for HgPathBuf {
     fn extend<T: IntoIterator<Item = u8>>(&mut self, iter: T) {
         self.inner.extend(iter);
     }
 }
 
 /// TODO: Once https://www.mercurial-scm.org/wiki/WindowsUTF8Plan is
 /// implemented, these conversion utils will have to work differently depending
 /// on the repository encoding: either `UTF-8` or `MBCS`.
 
 pub fn hg_path_to_os_string<P: AsRef<HgPath>>(
     hg_path: P,
 ) -> Result<OsString, HgPathError> {
     hg_path.as_ref().check_state()?;
     let os_str;
     #[cfg(unix)]
     {
         use std::os::unix::ffi::OsStrExt;
         os_str = std::ffi::OsStr::from_bytes(&hg_path.as_ref().as_bytes());
     }
     // TODO Handle other platforms
     // TODO: convert from WTF8 to Windows MBCS (ANSI encoding).
     Ok(os_str.to_os_string())
 }
 
 pub fn hg_path_to_path_buf<P: AsRef<HgPath>>(
     hg_path: P,
 ) -> Result<PathBuf, HgPathError> {
     Ok(Path::new(&hg_path_to_os_string(hg_path)?).to_path_buf())
 }
 
 pub fn os_string_to_hg_path_buf<S: AsRef<OsStr>>(
     os_string: S,
 ) -> Result<HgPathBuf, HgPathError> {
     let buf;
     #[cfg(unix)]
     {
         use std::os::unix::ffi::OsStrExt;
         buf = HgPathBuf::from_bytes(&os_string.as_ref().as_bytes());
     }
     // TODO Handle other platforms
     // TODO: convert from WTF8 to Windows MBCS (ANSI encoding).
 
     buf.check_state()?;
     Ok(buf)
 }
 
 pub fn path_to_hg_path_buf<P: AsRef<Path>>(
     path: P,
 ) -> Result<HgPathBuf, HgPathError> {
     let buf;
     let os_str = path.as_ref().as_os_str();
     #[cfg(unix)]
     {
         use std::os::unix::ffi::OsStrExt;
         buf = HgPathBuf::from_bytes(&os_str.as_bytes());
     }
     // TODO Handle other platforms
     // TODO: convert from WTF8 to Windows MBCS (ANSI encoding).
 
     buf.check_state()?;
     Ok(buf)
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
     use pretty_assertions::assert_eq;
 
     #[test]
     fn test_path_states() {
         assert_eq!(
             Err(HgPathError::LeadingSlash(b"/".to_vec())),
             HgPath::new(b"/").check_state()
         );
         assert_eq!(
             Err(HgPathError::ConsecutiveSlashes {
                 bytes: b"a/b//c".to_vec(),
                 second_slash_index: 4
             }),
             HgPath::new(b"a/b//c").check_state()
         );
         assert_eq!(
             Err(HgPathError::ContainsNullByte {
                 bytes: b"a/b/\0c".to_vec(),
                 null_byte_index: 4
             }),
             HgPath::new(b"a/b/\0c").check_state()
         );
         // TODO test HgPathError::DecodeError for the Windows implementation.
         assert_eq!(true, HgPath::new(b"").is_valid());
         assert_eq!(true, HgPath::new(b"a/b/c").is_valid());
         // Backslashes in paths are not significant, but allowed
         assert_eq!(true, HgPath::new(br"a\b/c").is_valid());
         // Dots in paths are not significant, but allowed
         assert_eq!(true, HgPath::new(b"a/b/../c/").is_valid());
         assert_eq!(true, HgPath::new(b"./a/b/../c/").is_valid());
     }
 
     #[test]
     fn test_iter() {
         let path = HgPath::new(b"a");
         let mut iter = path.bytes();
         assert_eq!(Some(&b'a'), iter.next());
         assert_eq!(None, iter.next_back());
         assert_eq!(None, iter.next());
 
         let path = HgPath::new(b"a");
         let mut iter = path.bytes();
         assert_eq!(Some(&b'a'), iter.next_back());
         assert_eq!(None, iter.next_back());
         assert_eq!(None, iter.next());
 
         let path = HgPath::new(b"abc");
         let mut iter = path.bytes();
         assert_eq!(Some(&b'a'), iter.next());
         assert_eq!(Some(&b'c'), iter.next_back());
         assert_eq!(Some(&b'b'), iter.next_back());
         assert_eq!(None, iter.next_back());
         assert_eq!(None, iter.next());
 
         let path = HgPath::new(b"abc");
         let mut iter = path.bytes();
         assert_eq!(Some(&b'a'), iter.next());
         assert_eq!(Some(&b'b'), iter.next());
         assert_eq!(Some(&b'c'), iter.next());
         assert_eq!(None, iter.next_back());
         assert_eq!(None, iter.next());
 
         let path = HgPath::new(b"abc");
         let iter = path.bytes();
         let mut vec = Vec::new();
         vec.extend(iter);
         assert_eq!(vec![b'a', b'b', b'c'], vec);
 
         let path = HgPath::new(b"abc");
         let mut iter = path.bytes();
         assert_eq!(Some(2), iter.rposition(|c| *c == b'c'));
 
         let path = HgPath::new(b"abc");
         let mut iter = path.bytes();
         assert_eq!(None, iter.rposition(|c| *c == b'd'));
     }
 
     #[test]
     fn test_join() {
         let path = HgPathBuf::from_bytes(b"a").join(HgPath::new(b"b"));
         assert_eq!(b"a/b", path.as_bytes());
 
         let path = HgPathBuf::from_bytes(b"a/").join(HgPath::new(b"b/c"));
         assert_eq!(b"a/b/c", path.as_bytes());
 
         // No leading slash if empty before join
         let path = HgPathBuf::new().join(HgPath::new(b"b/c"));
         assert_eq!(b"b/c", path.as_bytes());
 
         // The leading slash is an invalid representation of an `HgPath`, but
         // it can happen. This creates another invalid representation of
         // consecutive bytes.
         // TODO What should be done in this case? Should we silently remove
         // the extra slash? Should we change the signature to a problematic
         // `Result<HgPathBuf, HgPathError>`, or should we just keep it so and
         // let the error happen upon filesystem interaction?
         let path = HgPathBuf::from_bytes(b"a/").join(HgPath::new(b"/b"));
         assert_eq!(b"a//b", path.as_bytes());
         let path = HgPathBuf::from_bytes(b"a").join(HgPath::new(b"/b"));
         assert_eq!(b"a//b", path.as_bytes());
     }
 
     #[test]
     fn test_relative_to() {
         let path = HgPath::new(b"");
         let base = HgPath::new(b"");
         assert_eq!(Some(path), path.relative_to(base));
 
         let path = HgPath::new(b"path");
         let base = HgPath::new(b"");
         assert_eq!(Some(path), path.relative_to(base));
 
         let path = HgPath::new(b"a");
         let base = HgPath::new(b"b");
         assert_eq!(None, path.relative_to(base));
 
         let path = HgPath::new(b"a/b");
         let base = HgPath::new(b"a");
         assert_eq!(None, path.relative_to(base));
 
         let path = HgPath::new(b"a/b");
         let base = HgPath::new(b"a/");
         assert_eq!(Some(HgPath::new(b"b")), path.relative_to(base));
 
         let path = HgPath::new(b"nested/path/to/b");
         let base = HgPath::new(b"nested/path/");
         assert_eq!(Some(HgPath::new(b"to/b")), path.relative_to(base));
 
         let path = HgPath::new(b"ends/with/dir/");
         let base = HgPath::new(b"ends/");
         assert_eq!(Some(HgPath::new(b"with/dir/")), path.relative_to(base));
     }
 
     #[test]
     #[cfg(unix)]
     fn test_split_drive() {
         // Taken from the Python stdlib's tests
         assert_eq!(
             HgPath::new(br"/foo/bar").split_drive(),
             (HgPath::new(b""), HgPath::new(br"/foo/bar"))
         );
         assert_eq!(
             HgPath::new(br"foo:bar").split_drive(),
             (HgPath::new(b""), HgPath::new(br"foo:bar"))
         );
         assert_eq!(
             HgPath::new(br":foo:bar").split_drive(),
             (HgPath::new(b""), HgPath::new(br":foo:bar"))
         );
         // Also try NT paths; should not split them
         assert_eq!(
             HgPath::new(br"c:\foo\bar").split_drive(),
             (HgPath::new(b""), HgPath::new(br"c:\foo\bar"))
         );
         assert_eq!(
             HgPath::new(b"c:/foo/bar").split_drive(),
             (HgPath::new(b""), HgPath::new(br"c:/foo/bar"))
         );
         assert_eq!(
             HgPath::new(br"\\conky\mountpoint\foo\bar").split_drive(),
             (
                 HgPath::new(b""),
                 HgPath::new(br"\\conky\mountpoint\foo\bar")
             )
         );
     }
 
     #[test]
     #[cfg(windows)]
     fn test_split_drive() {
         assert_eq!(
             HgPath::new(br"c:\foo\bar").split_drive(),
             (HgPath::new(br"c:"), HgPath::new(br"\foo\bar"))
         );
         assert_eq!(
             HgPath::new(b"c:/foo/bar").split_drive(),
             (HgPath::new(br"c:"), HgPath::new(br"/foo/bar"))
         );
         assert_eq!(
             HgPath::new(br"\\conky\mountpoint\foo\bar").split_drive(),
             (
                 HgPath::new(br"\\conky\mountpoint"),
                 HgPath::new(br"\foo\bar")
             )
         );
         assert_eq!(
             HgPath::new(br"//conky/mountpoint/foo/bar").split_drive(),
             (
                 HgPath::new(br"//conky/mountpoint"),
                 HgPath::new(br"/foo/bar")
             )
         );
         assert_eq!(
             HgPath::new(br"\\\conky\mountpoint\foo\bar").split_drive(),
             (
                 HgPath::new(br""),
                 HgPath::new(br"\\\conky\mountpoint\foo\bar")
             )
         );
         assert_eq!(
             HgPath::new(br"///conky/mountpoint/foo/bar").split_drive(),
             (
                 HgPath::new(br""),
                 HgPath::new(br"///conky/mountpoint/foo/bar")
             )
         );
         assert_eq!(
             HgPath::new(br"\\conky\\mountpoint\foo\bar").split_drive(),
             (
                 HgPath::new(br""),
                 HgPath::new(br"\\conky\\mountpoint\foo\bar")
             )
         );
         assert_eq!(
             HgPath::new(br"//conky//mountpoint/foo/bar").split_drive(),
             (
                 HgPath::new(br""),
                 HgPath::new(br"//conky//mountpoint/foo/bar")
             )
         );
         // UNC part containing U+0130
         assert_eq!(
             HgPath::new(b"//conky/MOUNTPO\xc4\xb0NT/foo/bar").split_drive(),
             (
                 HgPath::new(b"//conky/MOUNTPO\xc4\xb0NT"),
                 HgPath::new(br"/foo/bar")
             )
         );
     }
 
     #[test]
     fn test_parent() {
         let path = HgPath::new(b"");
         assert_eq!(path.parent(), path);
 
         let path = HgPath::new(b"a");
         assert_eq!(path.parent(), HgPath::new(b""));
 
         let path = HgPath::new(b"a/b");
         assert_eq!(path.parent(), HgPath::new(b"a"));
 
         let path = HgPath::new(b"a/other/b");
         assert_eq!(path.parent(), HgPath::new(b"a/other"));
     }
 }