rust-matchers: better support file_set in IntersectionMatcher

Previously, if both of the input matchers had non-exact file sets,
IntersectionMatcher would simply have an empty fileset.

Now, we duplicate Python behavior: we *union* the filesets of the
matchers in that case.  This makes some sense, because without exact
input file sets, we can't do an exact intersection and must
over-approximate.

Concretely, this is necessary because the file_set is the list of
files that were explicitly listed by the user, and we want to provide
explicit errors for all such files, from both matchers.

rust/hg-core/src/matchers.rs

@@ -1,1753 +1,1759 b''
 // matchers.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.
 
 //! Structs and types for matching files and directories.
 
 use crate::{
     dirstate::dirs_multiset::DirsChildrenMultiset,
     filepatterns::{
         build_single_regex, filter_subincludes, get_patterns_from_file,
         PatternFileWarning, PatternResult,
     },
     utils::{
         files::find_dirs,
         hg_path::{HgPath, HgPathBuf},
         Escaped,
     },
     DirsMultiset, DirstateMapError, FastHashMap, IgnorePattern, PatternError,
     PatternSyntax,
 };
 
 use crate::dirstate::status::IgnoreFnType;
 use crate::filepatterns::normalize_path_bytes;
 use std::borrow::ToOwned;
 use std::collections::HashSet;
 use std::fmt::{Display, Error, Formatter};
 use std::ops::Deref;
 use std::path::{Path, PathBuf};
 
 #[derive(Debug, PartialEq)]
 pub enum VisitChildrenSet {
     /// Don't visit anything
     Empty,
     /// Only visit this directory
     This,
     /// Visit this directory and these subdirectories
     /// TODO Should we implement a `NonEmptyHashSet`?
     Set(HashSet<HgPathBuf>),
     /// Visit this directory and all subdirectories
     Recursive,
 }
 
 pub trait Matcher: core::fmt::Debug {
     /// Explicitly listed files
     fn file_set(&self) -> Option<&HashSet<HgPathBuf>>;
     /// Returns whether `filename` is in `file_set`
     fn exact_match(&self, filename: &HgPath) -> bool;
     /// Returns whether `filename` is matched by this matcher
     fn matches(&self, filename: &HgPath) -> bool;
     /// Decides whether a directory should be visited based on whether it
     /// has potential matches in it or one of its subdirectories, and
     /// potentially lists which subdirectories of that directory should be
     /// visited. This is based on the match's primary, included, and excluded
     /// patterns.
     ///
     /// # Example
     ///
     /// Assume matchers `['path:foo/bar', 'rootfilesin:qux']`, we would
     /// return the following values (assuming the implementation of
     /// visit_children_set is capable of recognizing this; some implementations
     /// are not).
     ///
     /// ```text
     /// ```ignore
     /// '' -> {'foo', 'qux'}
     /// 'baz' -> set()
     /// 'foo' -> {'bar'}
     /// // Ideally this would be `Recursive`, but since the prefix nature of
     /// // matchers is applied to the entire matcher, we have to downgrade this
     /// // to `This` due to the (yet to be implemented in Rust) non-prefix
     /// // `RootFilesIn'-kind matcher being mixed in.
     /// 'foo/bar' -> 'this'
     /// 'qux' -> 'this'
     /// ```
     /// # Important
     ///
     /// Most matchers do not know if they're representing files or
     /// directories. They see `['path:dir/f']` and don't know whether `f` is a
     /// file or a directory, so `visit_children_set('dir')` for most matchers
     /// will return `HashSet{ HgPath { "f" } }`, but if the matcher knows it's
     /// a file (like the yet to be implemented in Rust `ExactMatcher` does),
     /// it may return `VisitChildrenSet::This`.
     /// Do not rely on the return being a `HashSet` indicating that there are
     /// no files in this dir to investigate (or equivalently that if there are
     /// files to investigate in 'dir' that it will always return
     /// `VisitChildrenSet::This`).
     fn visit_children_set(&self, directory: &HgPath) -> VisitChildrenSet;
     /// Matcher will match everything and `files_set()` will be empty:
     /// optimization might be possible.
     fn matches_everything(&self) -> bool;
     /// Matcher will match exactly the files in `files_set()`: optimization
     /// might be possible.
     fn is_exact(&self) -> bool;
 }
 
 /// Matches everything.
 ///```
 /// use hg::{ matchers::{Matcher, AlwaysMatcher}, utils::hg_path::HgPath };
 ///
 /// let matcher = AlwaysMatcher;
 ///
 /// assert_eq!(matcher.matches(HgPath::new(b"whatever")), true);
 /// assert_eq!(matcher.matches(HgPath::new(b"b.txt")), true);
 /// assert_eq!(matcher.matches(HgPath::new(b"main.c")), true);
 /// assert_eq!(matcher.matches(HgPath::new(br"re:.*\.c$")), true);
 /// ```
 #[derive(Debug)]
 pub struct AlwaysMatcher;
 
 impl Matcher for AlwaysMatcher {
     fn file_set(&self) -> Option<&HashSet<HgPathBuf>> {
         None
     }
     fn exact_match(&self, _filename: &HgPath) -> bool {
         false
     }
     fn matches(&self, _filename: &HgPath) -> bool {
         true
     }
     fn visit_children_set(&self, _directory: &HgPath) -> VisitChildrenSet {
         VisitChildrenSet::Recursive
     }
     fn matches_everything(&self) -> bool {
         true
     }
     fn is_exact(&self) -> bool {
         false
     }
 }
 
 /// Matches nothing.
 #[derive(Debug)]
 pub struct NeverMatcher;
 
 impl Matcher for NeverMatcher {
     fn file_set(&self) -> Option<&HashSet<HgPathBuf>> {
         None
     }
     fn exact_match(&self, _filename: &HgPath) -> bool {
         false
     }
     fn matches(&self, _filename: &HgPath) -> bool {
         false
     }
     fn visit_children_set(&self, _directory: &HgPath) -> VisitChildrenSet {
         VisitChildrenSet::Empty
     }
     fn matches_everything(&self) -> bool {
         false
     }
     fn is_exact(&self) -> bool {
         true
     }
 }
 
 /// Matches the input files exactly. They are interpreted as paths, not
 /// patterns.
 ///
 ///```
 /// use hg::{ matchers::{Matcher, FileMatcher}, utils::hg_path::{HgPath, HgPathBuf} };
 ///
 /// let files = vec![HgPathBuf::from_bytes(b"a.txt"), HgPathBuf::from_bytes(br"re:.*\.c$")];
 /// let matcher = FileMatcher::new(files).unwrap();
 ///
 /// assert_eq!(matcher.matches(HgPath::new(b"a.txt")), true);
 /// assert_eq!(matcher.matches(HgPath::new(b"b.txt")), false);
 /// assert_eq!(matcher.matches(HgPath::new(b"main.c")), false);
 /// assert_eq!(matcher.matches(HgPath::new(br"re:.*\.c$")), true);
 /// ```
 #[derive(Debug)]
 pub struct FileMatcher {
     files: HashSet<HgPathBuf>,
     dirs: DirsMultiset,
 }
 
 impl FileMatcher {
     pub fn new(files: Vec<HgPathBuf>) -> Result<Self, DirstateMapError> {
         let dirs = DirsMultiset::from_manifest(&files)?;
         Ok(Self {
             files: HashSet::from_iter(files.into_iter()),
             dirs,
         })
     }
     fn inner_matches(&self, filename: &HgPath) -> bool {
         self.files.contains(filename.as_ref())
     }
 }
 
 impl Matcher for FileMatcher {
     fn file_set(&self) -> Option<&HashSet<HgPathBuf>> {
         Some(&self.files)
     }
     fn exact_match(&self, filename: &HgPath) -> bool {
         self.inner_matches(filename)
     }
     fn matches(&self, filename: &HgPath) -> bool {
         self.inner_matches(filename)
     }
     fn visit_children_set(&self, directory: &HgPath) -> VisitChildrenSet {
         if self.files.is_empty() || !self.dirs.contains(&directory) {
             return VisitChildrenSet::Empty;
         }
         let mut candidates: HashSet<HgPathBuf> =
             self.dirs.iter().cloned().collect();
 
         candidates.extend(self.files.iter().cloned());
         candidates.remove(HgPath::new(b""));
 
         if !directory.as_ref().is_empty() {
             let directory = [directory.as_ref().as_bytes(), b"/"].concat();
             candidates = candidates
                 .iter()
                 .filter_map(|c| {
                     if c.as_bytes().starts_with(&directory) {
                         Some(HgPathBuf::from_bytes(
                             &c.as_bytes()[directory.len()..],
                         ))
                     } else {
                         None
                     }
                 })
                 .collect();
         }
 
         // `self.dirs` includes all of the directories, recursively, so if
         // we're attempting to match 'foo/bar/baz.txt', it'll have '', 'foo',
         // 'foo/bar' in it. Thus we can safely ignore a candidate that has a
         // '/' in it, indicating it's for a subdir-of-a-subdir; the immediate
         // subdir will be in there without a slash.
         VisitChildrenSet::Set(
             candidates
                 .into_iter()
                 .filter_map(|c| {
                     if c.bytes().all(|b| *b != b'/') {
                         Some(c)
                     } else {
                         None
                     }
                 })
                 .collect(),
         )
     }
     fn matches_everything(&self) -> bool {
         false
     }
     fn is_exact(&self) -> bool {
         true
     }
 }
 
 /// Matches files that are included in the ignore rules.
 /// ```
 /// use hg::{
 ///     matchers::{IncludeMatcher, Matcher},
 ///     IgnorePattern,
 ///     PatternSyntax,
 ///     utils::hg_path::HgPath
 /// };
 /// use std::path::Path;
 /// ///
 /// let ignore_patterns =
 /// vec![IgnorePattern::new(PatternSyntax::RootGlob, b"this*", Path::new(""))];
 /// let matcher = IncludeMatcher::new(ignore_patterns).unwrap();
 /// ///
 /// assert_eq!(matcher.matches(HgPath::new(b"testing")), false);
 /// assert_eq!(matcher.matches(HgPath::new(b"this should work")), true);
 /// assert_eq!(matcher.matches(HgPath::new(b"this also")), true);
 /// assert_eq!(matcher.matches(HgPath::new(b"but not this")), false);
 /// ```
 pub struct IncludeMatcher<'a> {
     patterns: Vec<u8>,
     match_fn: IgnoreFnType<'a>,
     /// Whether all the patterns match a prefix (i.e. recursively)
     prefix: bool,
     roots: HashSet<HgPathBuf>,
     dirs: HashSet<HgPathBuf>,
     parents: HashSet<HgPathBuf>,
 }
 
 impl core::fmt::Debug for IncludeMatcher<'_> {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("IncludeMatcher")
             .field("patterns", &String::from_utf8_lossy(&self.patterns))
             .field("prefix", &self.prefix)
             .field("roots", &self.roots)
             .field("dirs", &self.dirs)
             .field("parents", &self.parents)
             .finish()
     }
 }
 
 impl<'a> Matcher for IncludeMatcher<'a> {
     fn file_set(&self) -> Option<&HashSet<HgPathBuf>> {
         None
     }
 
     fn exact_match(&self, _filename: &HgPath) -> bool {
         false
     }
 
     fn matches(&self, filename: &HgPath) -> bool {
         (self.match_fn)(filename)
     }
 
     fn visit_children_set(&self, directory: &HgPath) -> VisitChildrenSet {
         let dir = directory;
         if self.prefix && self.roots.contains(dir) {
             return VisitChildrenSet::Recursive;
         }
         if self.roots.contains(HgPath::new(b""))
             || self.roots.contains(dir)
             || self.dirs.contains(dir)
             || find_dirs(dir).any(|parent_dir| self.roots.contains(parent_dir))
         {
             return VisitChildrenSet::This;
         }
 
         if self.parents.contains(dir.as_ref()) {
             let multiset = self.get_all_parents_children();
             if let Some(children) = multiset.get(dir) {
                 return VisitChildrenSet::Set(
                     children.iter().map(HgPathBuf::from).collect(),
                 );
             }
         }
         VisitChildrenSet::Empty
     }
 
     fn matches_everything(&self) -> bool {
         false
     }
 
     fn is_exact(&self) -> bool {
         false
     }
 }
 
 /// The union of multiple matchers. Will match if any of the matchers match.
 #[derive(Debug)]
 pub struct UnionMatcher {
     matchers: Vec<Box<dyn Matcher + Sync>>,
 }
 
 impl Matcher for UnionMatcher {
     fn file_set(&self) -> Option<&HashSet<HgPathBuf>> {
         None
     }
 
     fn exact_match(&self, _filename: &HgPath) -> bool {
         false
     }
 
     fn matches(&self, filename: &HgPath) -> bool {
         self.matchers.iter().any(|m| m.matches(filename))
     }
 
     fn visit_children_set(&self, directory: &HgPath) -> VisitChildrenSet {
         let mut result = HashSet::new();
         let mut this = false;
         for matcher in self.matchers.iter() {
             let visit = matcher.visit_children_set(directory);
             match visit {
                 VisitChildrenSet::Empty => continue,
                 VisitChildrenSet::This => {
                     this = true;
                     // Don't break, we might have an 'all' in here.
                     continue;
                 }
                 VisitChildrenSet::Set(set) => {
                     result.extend(set);
                 }
                 VisitChildrenSet::Recursive => {
                     return visit;
                 }
             }
         }
         if this {
             return VisitChildrenSet::This;
         }
         if result.is_empty() {
             VisitChildrenSet::Empty
         } else {
             VisitChildrenSet::Set(result)
         }
     }
 
     fn matches_everything(&self) -> bool {
         // TODO Maybe if all are AlwaysMatcher?
         false
     }
 
     fn is_exact(&self) -> bool {
         false
     }
 }
 
 impl UnionMatcher {
     pub fn new(matchers: Vec<Box<dyn Matcher + Sync>>) -> Self {
         Self { matchers }
     }
 }
 
 #[derive(Debug)]
 pub struct IntersectionMatcher {
     m1: Box<dyn Matcher + Sync>,
     m2: Box<dyn Matcher + Sync>,
     files: Option<HashSet<HgPathBuf>>,
 }
 
 impl Matcher for IntersectionMatcher {
     fn file_set(&self) -> Option<&HashSet<HgPathBuf>> {
         self.files.as_ref()
     }
 
     fn exact_match(&self, filename: &HgPath) -> bool {
         self.files.as_ref().map_or(false, |f| f.contains(filename))
     }
 
     fn matches(&self, filename: &HgPath) -> bool {
         self.m1.matches(filename) && self.m2.matches(filename)
     }
 
     fn visit_children_set(&self, directory: &HgPath) -> VisitChildrenSet {
         let m1_set = self.m1.visit_children_set(directory);
         if m1_set == VisitChildrenSet::Empty {
             return VisitChildrenSet::Empty;
         }
         let m2_set = self.m2.visit_children_set(directory);
         if m2_set == VisitChildrenSet::Empty {
             return VisitChildrenSet::Empty;
         }
 
         if m1_set == VisitChildrenSet::Recursive {
             return m2_set;
         } else if m2_set == VisitChildrenSet::Recursive {
             return m1_set;
         }
 
         match (&m1_set, &m2_set) {
             (VisitChildrenSet::Recursive, _) => m2_set,
             (_, VisitChildrenSet::Recursive) => m1_set,
             (VisitChildrenSet::This, _) | (_, VisitChildrenSet::This) => {
                 VisitChildrenSet::This
             }
             (VisitChildrenSet::Set(m1), VisitChildrenSet::Set(m2)) => {
                 let set: HashSet<_> = m1.intersection(m2).cloned().collect();
                 if set.is_empty() {
                     VisitChildrenSet::Empty
                 } else {
                     VisitChildrenSet::Set(set)
                 }
             }
             _ => unreachable!(),
         }
     }
 
     fn matches_everything(&self) -> bool {
         self.m1.matches_everything() && self.m2.matches_everything()
     }
 
     fn is_exact(&self) -> bool {
         self.m1.is_exact() || self.m2.is_exact()
     }
 }
 
 impl IntersectionMatcher {
     pub fn new(
         mut m1: Box<dyn Matcher + Sync>,
         mut m2: Box<dyn Matcher + Sync>,
     ) -> Self {
         let files = if m1.is_exact() || m2.is_exact() {
             if !m1.is_exact() {
                 std::mem::swap(&mut m1, &mut m2);
             }
             m1.file_set().map(|m1_files| {
                 m1_files.iter().cloned().filter(|f| m2.matches(f)).collect()
             })
         } else {
-            None
+            // without exact input file sets, we can't do an exact
+            // intersection, so we must over-approximate by
+            // unioning instead
+            m1.file_set().map(|m1_files| match m2.file_set() {
+                Some(m2_files) => m1_files.union(m2_files).cloned().collect(),
+                None => m1_files.iter().cloned().collect(),
+            })
         };
         Self { m1, m2, files }
     }
 }
 
 #[derive(Debug)]
 pub struct DifferenceMatcher {
     base: Box<dyn Matcher + Sync>,
     excluded: Box<dyn Matcher + Sync>,
     files: Option<HashSet<HgPathBuf>>,
 }
 
 impl Matcher for DifferenceMatcher {
     fn file_set(&self) -> Option<&HashSet<HgPathBuf>> {
         self.files.as_ref()
     }
 
     fn exact_match(&self, filename: &HgPath) -> bool {
         self.files.as_ref().map_or(false, |f| f.contains(filename))
     }
 
     fn matches(&self, filename: &HgPath) -> bool {
         self.base.matches(filename) && !self.excluded.matches(filename)
     }
 
     fn visit_children_set(&self, directory: &HgPath) -> VisitChildrenSet {
         let excluded_set = self.excluded.visit_children_set(directory);
         if excluded_set == VisitChildrenSet::Recursive {
             return VisitChildrenSet::Empty;
         }
         let base_set = self.base.visit_children_set(directory);
         // Possible values for base: 'recursive', 'this', set(...), set()
         // Possible values for excluded:          'this', set(...), set()
         // If excluded has nothing under here that we care about, return base,
         // even if it's 'recursive'.
         if excluded_set == VisitChildrenSet::Empty {
             return base_set;
         }
         match base_set {
             VisitChildrenSet::This | VisitChildrenSet::Recursive => {
                 // Never return 'recursive' here if excluded_set is any kind of
                 // non-empty (either 'this' or set(foo)), since excluded might
                 // return set() for a subdirectory.
                 VisitChildrenSet::This
             }
             set => {
                 // Possible values for base:         set(...), set()
                 // Possible values for excluded: 'this', set(...)
                 // We ignore excluded set results. They're possibly incorrect:
                 //  base = path:dir/subdir
                 //  excluded=rootfilesin:dir,
                 //  visit_children_set(''):
                 //   base returns {'dir'}, excluded returns {'dir'}, if we
                 //   subtracted we'd return set(), which is *not* correct, we
                 //   still need to visit 'dir'!
                 set
             }
         }
     }
 
     fn matches_everything(&self) -> bool {
         false
     }
 
     fn is_exact(&self) -> bool {
         self.base.is_exact()
     }
 }
 
 impl DifferenceMatcher {
     pub fn new(
         base: Box<dyn Matcher + Sync>,
         excluded: Box<dyn Matcher + Sync>,
     ) -> Self {
         let base_is_exact = base.is_exact();
         let base_files = base.file_set().map(ToOwned::to_owned);
         let mut new = Self {
             base,
             excluded,
             files: None,
         };
         if base_is_exact {
             new.files = base_files.map(|files| {
                 files.iter().cloned().filter(|f| new.matches(f)).collect()
             });
         }
         new
     }
 }
 
 /// Wraps [`regex::bytes::Regex`] to improve performance in multithreaded
 /// contexts.
 ///
 /// The `status` algorithm makes heavy use of threads, and calling `is_match`
 /// from many threads at once is prone to contention, probably within the
 /// scratch space needed as the regex DFA is built lazily.
 ///
 /// We are in the process of raising the issue upstream, but for now
 /// the workaround used here is to store the `Regex` in a lazily populated
 /// thread-local variable, sharing the initial read-only compilation, but
 /// not the lazy dfa scratch space mentioned above.
 ///
 /// This reduces the contention observed with 16+ threads, but does not
 /// completely remove it. Hopefully this can be addressed upstream.
 struct RegexMatcher {
     /// Compiled at the start of the status algorithm, used as a base for
     /// cloning in each thread-local `self.local`, thus sharing the expensive
     /// first compilation.
     base: regex::bytes::Regex,
     /// Thread-local variable that holds the `Regex` that is actually queried
     /// from each thread.
     local: thread_local::ThreadLocal<regex::bytes::Regex>,
 }
 
 impl RegexMatcher {
     /// Returns whether the path matches the stored `Regex`.
     pub fn is_match(&self, path: &HgPath) -> bool {
         self.local
             .get_or(|| self.base.clone())
             .is_match(path.as_bytes())
     }
 }
 
 /// Returns a function that matches an `HgPath` against the given regex
 /// pattern.
 ///
 /// This can fail when the pattern is invalid or not supported by the
 /// underlying engine (the `regex` crate), for instance anything with
 /// back-references.
 #[logging_timer::time("trace")]
 fn re_matcher(pattern: &[u8]) -> PatternResult<RegexMatcher> {
     use std::io::Write;
 
     // The `regex` crate adds `.*` to the start and end of expressions if there
     // are no anchors, so add the start anchor.
     let mut escaped_bytes = vec![b'^', b'(', b'?', b':'];
     for byte in pattern {
         if *byte > 127 {
             write!(escaped_bytes, "\\x{:x}", *byte).unwrap();
         } else {
             escaped_bytes.push(*byte);
         }
     }
     escaped_bytes.push(b')');
 
     // Avoid the cost of UTF8 checking
     //
     // # Safety
     // This is safe because we escaped all non-ASCII bytes.
     let pattern_string = unsafe { String::from_utf8_unchecked(escaped_bytes) };
     let re = regex::bytes::RegexBuilder::new(&pattern_string)
         .unicode(false)
         // Big repos with big `.hgignore` will hit the default limit and
         // incur a significant performance hit. One repo's `hg status` hit
         // multiple *minutes*.
         .dfa_size_limit(50 * (1 << 20))
         .build()
         .map_err(|e| PatternError::UnsupportedSyntax(e.to_string()))?;
 
     Ok(RegexMatcher {
         base: re,
         local: Default::default(),
     })
 }
 
 /// Returns the regex pattern and a function that matches an `HgPath` against
 /// said regex formed by the given ignore patterns.
 fn build_regex_match<'a, 'b>(
     ignore_patterns: &'a [IgnorePattern],
 ) -> PatternResult<(Vec<u8>, IgnoreFnType<'b>)> {
     let mut regexps = vec![];
     let mut exact_set = HashSet::new();
 
     for pattern in ignore_patterns {
         if let Some(re) = build_single_regex(pattern)? {
             regexps.push(re);
         } else {
             let exact = normalize_path_bytes(&pattern.pattern);
             exact_set.insert(HgPathBuf::from_bytes(&exact));
         }
     }
 
     let full_regex = regexps.join(&b'|');
 
     // An empty pattern would cause the regex engine to incorrectly match the
     // (empty) root directory
     let func = if !(regexps.is_empty()) {
         let matcher = re_matcher(&full_regex)?;
         let func = move |filename: &HgPath| {
             exact_set.contains(filename) || matcher.is_match(filename)
         };
         Box::new(func) as IgnoreFnType
     } else {
         let func = move |filename: &HgPath| exact_set.contains(filename);
         Box::new(func) as IgnoreFnType
     };
 
     Ok((full_regex, func))
 }
 
 /// Returns roots and directories corresponding to each pattern.
 ///
 /// This calculates the roots and directories exactly matching the patterns and
 /// returns a tuple of (roots, dirs). It does not return other directories
 /// which may also need to be considered, like the parent directories.
 fn roots_and_dirs(
     ignore_patterns: &[IgnorePattern],
 ) -> (Vec<HgPathBuf>, Vec<HgPathBuf>) {
     let mut roots = Vec::new();
     let mut dirs = Vec::new();
 
     for ignore_pattern in ignore_patterns {
         let IgnorePattern {
             syntax, pattern, ..
         } = ignore_pattern;
         match syntax {
             PatternSyntax::RootGlob | PatternSyntax::Glob => {
                 let mut root = HgPathBuf::new();
                 for p in pattern.split(|c| *c == b'/') {
                     if p.iter()
                         .any(|c| matches!(*c, b'[' | b'{' | b'*' | b'?'))
                     {
                         break;
                     }
                     root.push(HgPathBuf::from_bytes(p).as_ref());
                 }
                 roots.push(root);
             }
             PatternSyntax::Path
             | PatternSyntax::RelPath
             | PatternSyntax::FilePath => {
                 let pat = HgPath::new(if pattern == b"." {
                     &[] as &[u8]
                 } else {
                     pattern
                 });
                 roots.push(pat.to_owned());
             }
             PatternSyntax::RootFiles => {
                 let pat = if pattern == b"." {
                     &[] as &[u8]
                 } else {
                     pattern
                 };
                 dirs.push(HgPathBuf::from_bytes(pat));
             }
             _ => {
                 roots.push(HgPathBuf::new());
             }
         }
     }
     (roots, dirs)
 }
 
 /// Paths extracted from patterns
 #[derive(Debug, PartialEq)]
 struct RootsDirsAndParents {
     /// Directories to match recursively
     pub roots: HashSet<HgPathBuf>,
     /// Directories to match non-recursively
     pub dirs: HashSet<HgPathBuf>,
     /// Implicitly required directories to go to items in either roots or dirs
     pub parents: HashSet<HgPathBuf>,
 }
 
 /// Extract roots, dirs and parents from patterns.
 fn roots_dirs_and_parents(
     ignore_patterns: &[IgnorePattern],
 ) -> PatternResult<RootsDirsAndParents> {
     let (roots, dirs) = roots_and_dirs(ignore_patterns);
 
     let mut parents = HashSet::new();
 
     parents.extend(
         DirsMultiset::from_manifest(&dirs)
             .map_err(|e| match e {
                 DirstateMapError::InvalidPath(e) => e,
                 _ => unreachable!(),
             })?
             .iter()
             .map(ToOwned::to_owned),
     );
     parents.extend(
         DirsMultiset::from_manifest(&roots)
             .map_err(|e| match e {
                 DirstateMapError::InvalidPath(e) => e,
                 _ => unreachable!(),
             })?
             .iter()
             .map(ToOwned::to_owned),
     );
 
     Ok(RootsDirsAndParents {
         roots: HashSet::from_iter(roots),
         dirs: HashSet::from_iter(dirs),
         parents,
     })
 }
 
 /// Returns a function that checks whether a given file (in the general sense)
 /// should be matched.
 fn build_match<'a>(
     ignore_patterns: Vec<IgnorePattern>,
 ) -> PatternResult<(Vec<u8>, IgnoreFnType<'a>)> {
     let mut match_funcs: Vec<IgnoreFnType<'a>> = vec![];
     // For debugging and printing
     let mut patterns = vec![];
 
     let (subincludes, ignore_patterns) = filter_subincludes(ignore_patterns)?;
 
     if !subincludes.is_empty() {
         // Build prefix-based matcher functions for subincludes
         let mut submatchers = FastHashMap::default();
         let mut prefixes = vec![];
 
         for sub_include in subincludes {
             let matcher = IncludeMatcher::new(sub_include.included_patterns)?;
             let match_fn =
                 Box::new(move |path: &HgPath| matcher.matches(path));
             prefixes.push(sub_include.prefix.clone());
             submatchers.insert(sub_include.prefix.clone(), match_fn);
         }
 
         let match_subinclude = move |filename: &HgPath| {
             for prefix in prefixes.iter() {
                 if let Some(rel) = filename.relative_to(prefix) {
                     if (submatchers[prefix])(rel) {
                         return true;
                     }
                 }
             }
             false
         };
 
         match_funcs.push(Box::new(match_subinclude));
     }
 
     if !ignore_patterns.is_empty() {
         // Either do dumb matching if all patterns are rootfiles, or match
         // with a regex.
         if ignore_patterns
             .iter()
             .all(|k| k.syntax == PatternSyntax::RootFiles)
         {
             let dirs: HashSet<_> = ignore_patterns
                 .iter()
                 .map(|k| k.pattern.to_owned())
                 .collect();
             let mut dirs_vec: Vec<_> = dirs.iter().cloned().collect();
 
             let match_func = move |path: &HgPath| -> bool {
                 let path = path.as_bytes();
                 let i = path.iter().rfind(|a| **a == b'/');
                 let dir = if let Some(i) = i {
                     &path[..*i as usize]
                 } else {
                     b"."
                 };
                 dirs.contains(dir.deref())
             };
             match_funcs.push(Box::new(match_func));
 
             patterns.extend(b"rootfilesin: ");
             dirs_vec.sort();
             patterns.extend(dirs_vec.escaped_bytes());
         } else {
             let (new_re, match_func) = build_regex_match(&ignore_patterns)?;
             patterns = new_re;
             match_funcs.push(match_func)
         }
     }
 
     Ok(if match_funcs.len() == 1 {
         (patterns, match_funcs.remove(0))
     } else {
         (
             patterns,
             Box::new(move |f: &HgPath| -> bool {
                 match_funcs.iter().any(|match_func| match_func(f))
             }),
         )
     })
 }
 
 /// Parses all "ignore" files with their recursive includes and returns a
 /// function that checks whether a given file (in the general sense) should be
 /// ignored.
 pub fn get_ignore_matcher<'a>(
     mut all_pattern_files: Vec<PathBuf>,
     root_dir: &Path,
     inspect_pattern_bytes: &mut impl FnMut(&Path, &[u8]),
 ) -> PatternResult<(IncludeMatcher<'a>, Vec<PatternFileWarning>)> {
     let mut all_patterns = vec![];
     let mut all_warnings = vec![];
 
     // Sort to make the ordering of calls to `inspect_pattern_bytes`
     // deterministic even if the ordering of `all_pattern_files` is not (such
     // as when a iteration order of a Python dict or Rust HashMap is involved).
     // Sort by "string" representation instead of the default by component
     // (with a Rust-specific definition of a component)
     all_pattern_files
         .sort_unstable_by(|a, b| a.as_os_str().cmp(b.as_os_str()));
 
     for pattern_file in &all_pattern_files {
         let (patterns, warnings) = get_patterns_from_file(
             pattern_file,
             root_dir,
             inspect_pattern_bytes,
         )?;
 
         all_patterns.extend(patterns.to_owned());
         all_warnings.extend(warnings);
     }
     let matcher = IncludeMatcher::new(all_patterns)?;
     Ok((matcher, all_warnings))
 }
 
 /// Parses all "ignore" files with their recursive includes and returns a
 /// function that checks whether a given file (in the general sense) should be
 /// ignored.
 pub fn get_ignore_function<'a>(
     all_pattern_files: Vec<PathBuf>,
     root_dir: &Path,
     inspect_pattern_bytes: &mut impl FnMut(&Path, &[u8]),
 ) -> PatternResult<(IgnoreFnType<'a>, Vec<PatternFileWarning>)> {
     let res =
         get_ignore_matcher(all_pattern_files, root_dir, inspect_pattern_bytes);
     res.map(|(matcher, all_warnings)| {
         let res: IgnoreFnType<'a> =
             Box::new(move |path: &HgPath| matcher.matches(path));
 
         (res, all_warnings)
     })
 }
 
 impl<'a> IncludeMatcher<'a> {
     pub fn new(ignore_patterns: Vec<IgnorePattern>) -> PatternResult<Self> {
         let RootsDirsAndParents {
             roots,
             dirs,
             parents,
         } = roots_dirs_and_parents(&ignore_patterns)?;
         let prefix = ignore_patterns.iter().all(|k| {
             matches!(k.syntax, PatternSyntax::Path | PatternSyntax::RelPath)
         });
         let (patterns, match_fn) = build_match(ignore_patterns)?;
 
         Ok(Self {
             patterns,
             match_fn,
             prefix,
             roots,
             dirs,
             parents,
         })
     }
 
     fn get_all_parents_children(&self) -> DirsChildrenMultiset {
         // TODO cache
         let thing = self
             .dirs
             .iter()
             .chain(self.roots.iter())
             .chain(self.parents.iter());
         DirsChildrenMultiset::new(thing, Some(&self.parents))
     }
 
     pub fn debug_get_patterns(&self) -> &[u8] {
         self.patterns.as_ref()
     }
 }
 
 impl<'a> Display for IncludeMatcher<'a> {
     fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error> {
         // XXX What about exact matches?
         // I'm not sure it's worth it to clone the HashSet and keep it
         // around just in case someone wants to display the matcher, plus
         // it's going to be unreadable after a few entries, but we need to
         // inform in this display that exact matches are being used and are
         // (on purpose) missing from the `includes`.
         write!(
             f,
             "IncludeMatcher(includes='{}')",
             String::from_utf8_lossy(&self.patterns.escaped_bytes())
         )
     }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
     use pretty_assertions::assert_eq;
     use std::path::Path;
 
     #[test]
     fn test_roots_and_dirs() {
         let pats = vec![
             IgnorePattern::new(PatternSyntax::Glob, b"g/h/*", Path::new("")),
             IgnorePattern::new(PatternSyntax::Glob, b"g/h", Path::new("")),
             IgnorePattern::new(PatternSyntax::Glob, b"g*", Path::new("")),
         ];
         let (roots, dirs) = roots_and_dirs(&pats);
 
         assert_eq!(
             roots,
             vec!(
                 HgPathBuf::from_bytes(b"g/h"),
                 HgPathBuf::from_bytes(b"g/h"),
                 HgPathBuf::new()
             ),
         );
         assert_eq!(dirs, vec!());
     }
 
     #[test]
     fn test_roots_dirs_and_parents() {
         let pats = vec![
             IgnorePattern::new(PatternSyntax::Glob, b"g/h/*", Path::new("")),
             IgnorePattern::new(PatternSyntax::Glob, b"g/h", Path::new("")),
             IgnorePattern::new(PatternSyntax::Glob, b"g*", Path::new("")),
         ];
 
         let mut roots = HashSet::new();
         roots.insert(HgPathBuf::from_bytes(b"g/h"));
         roots.insert(HgPathBuf::new());
 
         let dirs = HashSet::new();
 
         let mut parents = HashSet::new();
         parents.insert(HgPathBuf::new());
         parents.insert(HgPathBuf::from_bytes(b"g"));
 
         assert_eq!(
             roots_dirs_and_parents(&pats).unwrap(),
             RootsDirsAndParents {
                 roots,
                 dirs,
                 parents
             }
         );
     }
 
     #[test]
     fn test_filematcher_visit_children_set() {
         // Visitchildrenset
         let files = vec![HgPathBuf::from_bytes(b"dir/subdir/foo.txt")];
         let matcher = FileMatcher::new(files).unwrap();
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"subdir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::Set(set)
         );
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"foo.txt"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Set(set)
         );
 
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/foo.txt")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
     }
 
     #[test]
     fn test_filematcher_visit_children_set_files_and_dirs() {
         let files = vec![
             HgPathBuf::from_bytes(b"rootfile.txt"),
             HgPathBuf::from_bytes(b"a/file1.txt"),
             HgPathBuf::from_bytes(b"a/b/file2.txt"),
             // No file in a/b/c
             HgPathBuf::from_bytes(b"a/b/c/d/file4.txt"),
         ];
         let matcher = FileMatcher::new(files).unwrap();
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"a"));
         set.insert(HgPathBuf::from_bytes(b"rootfile.txt"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"b"));
         set.insert(HgPathBuf::from_bytes(b"file1.txt"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"a")),
             VisitChildrenSet::Set(set)
         );
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"c"));
         set.insert(HgPathBuf::from_bytes(b"file2.txt"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"a/b")),
             VisitChildrenSet::Set(set)
         );
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"d"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"a/b/c")),
             VisitChildrenSet::Set(set)
         );
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"file4.txt"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"a/b/c/d")),
             VisitChildrenSet::Set(set)
         );
 
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"a/b/c/d/e")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
     }
 
     #[test]
     fn test_includematcher() {
         // VisitchildrensetPrefix
         let matcher = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::RelPath,
             b"dir/subdir",
             Path::new(""),
         )])
         .unwrap();
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"subdir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::Set(set)
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Recursive
         );
         // OPT: This should probably be 'all' if its parent is?
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::This
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
 
         // VisitchildrensetRootfilesin
         let matcher = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::RootFiles,
             b"dir/subdir",
             Path::new(""),
         )])
         .unwrap();
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"subdir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::Set(set)
         );
 
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::This
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
 
         // VisitchildrensetGlob
         let matcher = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::Glob,
             b"dir/z*",
             Path::new(""),
         )])
         .unwrap();
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::This
         );
         // OPT: these should probably be set().
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::This
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::This
         );
 
         // VisitchildrensetFilePath
         let matcher = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::FilePath,
             b"dir/z",
             Path::new(""),
         )])
         .unwrap();
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"z"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::Set(set)
         );
         // OPT: these should probably be set().
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::Empty
         );
 
         // Test multiple patterns
         let matcher = IncludeMatcher::new(vec![
             IgnorePattern::new(PatternSyntax::RelPath, b"foo", Path::new("")),
             IgnorePattern::new(PatternSyntax::Glob, b"g*", Path::new("")),
         ])
         .unwrap();
 
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::This
         );
 
         // Test multiple patterns
         let matcher = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::Glob,
             b"**/*.exe",
             Path::new(""),
         )])
         .unwrap();
 
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::This
         );
     }
 
     #[test]
     fn test_unionmatcher() {
         // Path + Rootfiles
         let m1 = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::RelPath,
             b"dir/subdir",
             Path::new(""),
         )])
         .unwrap();
         let m2 = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::RootFiles,
             b"dir",
             Path::new(""),
         )])
         .unwrap();
         let matcher = UnionMatcher::new(vec![Box::new(m1), Box::new(m2)]);
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::This
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Recursive
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/foo")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
 
         // OPT: These next two could be 'all' instead of 'this'.
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/z")),
             VisitChildrenSet::This
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::This
         );
 
         // Path + unrelated Path
         let m1 = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::RelPath,
             b"dir/subdir",
             Path::new(""),
         )])
         .unwrap();
         let m2 = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::RelPath,
             b"folder",
             Path::new(""),
         )])
         .unwrap();
         let matcher = UnionMatcher::new(vec![Box::new(m1), Box::new(m2)]);
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"folder"));
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"subdir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::Set(set)
         );
 
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Recursive
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/foo")),
             VisitChildrenSet::Empty
         );
 
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Recursive
         );
         // OPT: These next two could be 'all' instead of 'this'.
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/z")),
             VisitChildrenSet::This
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::This
         );
 
         // Path + subpath
         let m1 = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::RelPath,
             b"dir/subdir/x",
             Path::new(""),
         )])
         .unwrap();
         let m2 = IncludeMatcher::new(vec![IgnorePattern::new(
             PatternSyntax::RelPath,
             b"dir/subdir",
             Path::new(""),
         )])
         .unwrap();
         let matcher = UnionMatcher::new(vec![Box::new(m1), Box::new(m2)]);
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"subdir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::Set(set)
         );
 
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Recursive
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/foo")),
             VisitChildrenSet::Empty
         );
 
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::Recursive
         );
         // OPT: this should probably be 'all' not 'this'.
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/z")),
             VisitChildrenSet::This
         );
     }
 
     #[test]
     fn test_intersectionmatcher() {
         // Include path + Include rootfiles
         let m1 = Box::new(
             IncludeMatcher::new(vec![IgnorePattern::new(
                 PatternSyntax::RelPath,
                 b"dir/subdir",
                 Path::new(""),
             )])
             .unwrap(),
         );
         let m2 = Box::new(
             IncludeMatcher::new(vec![IgnorePattern::new(
                 PatternSyntax::RootFiles,
                 b"dir",
                 Path::new(""),
             )])
             .unwrap(),
         );
         let matcher = IntersectionMatcher::new(m1, m2);
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::This
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/foo")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/z")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::Empty
         );
 
         // Non intersecting paths
         let m1 = Box::new(
             IncludeMatcher::new(vec![IgnorePattern::new(
                 PatternSyntax::RelPath,
                 b"dir/subdir",
                 Path::new(""),
             )])
             .unwrap(),
         );
         let m2 = Box::new(
             IncludeMatcher::new(vec![IgnorePattern::new(
                 PatternSyntax::RelPath,
                 b"folder",
                 Path::new(""),
             )])
             .unwrap(),
         );
         let matcher = IntersectionMatcher::new(m1, m2);
 
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/foo")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/z")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::Empty
         );
 
         // Nested paths
         let m1 = Box::new(
             IncludeMatcher::new(vec![IgnorePattern::new(
                 PatternSyntax::RelPath,
                 b"dir/subdir/x",
                 Path::new(""),
             )])
             .unwrap(),
         );
         let m2 = Box::new(
             IncludeMatcher::new(vec![IgnorePattern::new(
                 PatternSyntax::RelPath,
                 b"dir/subdir",
                 Path::new(""),
             )])
             .unwrap(),
         );
         let matcher = IntersectionMatcher::new(m1, m2);
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"subdir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::Set(set)
         );
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"x"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Set(set)
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/foo")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/z")),
             VisitChildrenSet::Empty
         );
         // OPT: this should probably be 'all' not 'this'.
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::This
         );
 
         // Diverging paths
         let m1 = Box::new(
             IncludeMatcher::new(vec![IgnorePattern::new(
                 PatternSyntax::RelPath,
                 b"dir/subdir/x",
                 Path::new(""),
             )])
             .unwrap(),
         );
         let m2 = Box::new(
             IncludeMatcher::new(vec![IgnorePattern::new(
                 PatternSyntax::RelPath,
                 b"dir/subdir/z",
                 Path::new(""),
             )])
             .unwrap(),
         );
         let matcher = IntersectionMatcher::new(m1, m2);
 
         // OPT: these next two could probably be Empty as well.
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
         // OPT: these next two could probably be Empty as well.
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"subdir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::Set(set)
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/foo")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/z")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::Empty
         );
     }
 
     #[test]
     fn test_differencematcher() {
         // Two alwaysmatchers should function like a nevermatcher
         let m1 = AlwaysMatcher;
         let m2 = AlwaysMatcher;
         let matcher = DifferenceMatcher::new(Box::new(m1), Box::new(m2));
 
         for case in &[
             &b""[..],
             b"dir",
             b"dir/subdir",
             b"dir/subdir/z",
             b"dir/foo",
             b"dir/subdir/x",
             b"folder",
         ] {
             assert_eq!(
                 matcher.visit_children_set(HgPath::new(case)),
                 VisitChildrenSet::Empty
             );
         }
 
         // One always and one never should behave the same as an always
         let m1 = AlwaysMatcher;
         let m2 = NeverMatcher;
         let matcher = DifferenceMatcher::new(Box::new(m1), Box::new(m2));
 
         for case in &[
             &b""[..],
             b"dir",
             b"dir/subdir",
             b"dir/subdir/z",
             b"dir/foo",
             b"dir/subdir/x",
             b"folder",
         ] {
             assert_eq!(
                 matcher.visit_children_set(HgPath::new(case)),
                 VisitChildrenSet::Recursive
             );
         }
 
         // Two include matchers
         let m1 = Box::new(
             IncludeMatcher::new(vec![IgnorePattern::new(
                 PatternSyntax::RelPath,
                 b"dir/subdir",
                 Path::new("/repo"),
             )])
             .unwrap(),
         );
         let m2 = Box::new(
             IncludeMatcher::new(vec![IgnorePattern::new(
                 PatternSyntax::RootFiles,
                 b"dir",
                 Path::new("/repo"),
             )])
             .unwrap(),
         );
 
         let matcher = DifferenceMatcher::new(m1, m2);
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"dir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"")),
             VisitChildrenSet::Set(set)
         );
 
         let mut set = HashSet::new();
         set.insert(HgPathBuf::from_bytes(b"subdir"));
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir")),
             VisitChildrenSet::Set(set)
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir")),
             VisitChildrenSet::Recursive
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/foo")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"folder")),
             VisitChildrenSet::Empty
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/z")),
             VisitChildrenSet::This
         );
         assert_eq!(
             matcher.visit_children_set(HgPath::new(b"dir/subdir/x")),
             VisitChildrenSet::This
         );
     }
 }