feat: Add directory lookup, as well as ignore-case capabilities.

This is needed to be able to refer from an entry on disk to the index,
and figure out if the index already has such entry.

New methods are:

* File::entry_by_path_icase
* File::prefixed_entry_range_icase
* File::entry_by_path_and_stage_icase
* File::directory_kind_by_path_icase

Author: Byron

crate-status.md

@@ -628,6 +628,7 @@ The git staging area.
     * [x] 'link' base indices to take information from, split index
     * [x] 'sdir' [sparse directory entries](https://github.blog/2021-08-16-highlights-from-git-2-33/) - marker
   * [x] verification of entries and extensions as well as checksum
+  * [ ] expand sparse directory entries using information of the tree itself
 * write
   * [x] V2
   * [x] V3 - extension bits
@@ -654,7 +655,7 @@ The git staging area.
     * [ ] IEOT index entry offset table
     * [ ] 'link' base indices to take information from, split index
     * [ ] 'sdir' sparse directory entries
-* add and remove entries
+* [ ] add and remove entries
 * [x] API documentation
     * [ ] Some examples
 

gix-index/src/access/mod.rs

@@ -3,7 +3,7 @@ use std::{cmp::Ordering, ops::Range};
 use bstr::{BStr, ByteSlice, ByteVec};
 use filetime::FileTime;
 
-use crate::{entry, extension, Entry, PathStorage, PathStorageRef, State, Version};
+use crate::{entry, extension, DirectoryKind, Entry, PathStorage, PathStorageRef, State, Version};
 
 // TODO: integrate this somehow, somewhere, depending on later usage.
 #[allow(dead_code)]
@@ -84,6 +84,38 @@ impl State {
         self.entry_index_by_idx_and_stage(path, idx, stage, stage_cmp)
     }
 
+    /// Find the entry index in [`entries()`][State::entries()] matching the given repository-relative
+    /// `path` and `stage`, or `None`.
+    /// If `ignore_case` is `true`, a case-insensitive (ASCII-folding only) search will be performed.
+    ///
+    /// Note that if there are ambiguities, like `x` and `X` being present in the index, any of these will be returned,
+    /// deterministically.
+    ///
+    /// Use the index for accessing multiple stages if they exists, but at least the single matching entry.
+    pub fn entry_index_by_path_and_stage_icase(
+        &self,
+        path: &BStr,
+        stage: entry::Stage,
+        ignore_case: bool,
+    ) -> Option<usize> {
+        if ignore_case {
+            let mut stage_cmp = Ordering::Equal;
+            let idx = self
+                .entries
+                .binary_search_by(|e| {
+                    let res = icase_cmp(e.path(self), path);
+                    if res.is_eq() {
+                        stage_cmp = e.stage().cmp(&stage);
+                    }
+                    res
+                })
+                .ok()?;
+            self.entry_index_by_idx_and_stage_icase(path, idx, stage, stage_cmp)
+        } else {
+            self.entry_index_by_path_and_stage(path, stage)
+        }
+    }
+
     /// Walk as far in `direction` as possible, with [`Ordering::Greater`] towards higher stages, and [`Ordering::Less`]
     /// towards lower stages, and return the lowest or highest seen stage.
     /// Return `None` if there is no greater or smaller stage.
@@ -108,6 +140,30 @@ impl State {
         }
     }
 
+    /// Walk as far in `direction` as possible, with [`Ordering::Greater`] towards higher stages, and [`Ordering::Less`]
+    /// towards lower stages, and return the lowest or highest seen stage.
+    /// Return `None` if there is no greater or smaller stage.
+    fn walk_entry_stages_icase(&self, path: &BStr, base: usize, direction: Ordering) -> Option<usize> {
+        match direction {
+            Ordering::Greater => self
+                .entries
+                .get(base + 1..)?
+                .iter()
+                .enumerate()
+                .take_while(|(_, e)| e.path(self).eq_ignore_ascii_case(path))
+                .last()
+                .map(|(idx, _)| base + 1 + idx),
+            Ordering::Equal => Some(base),
+            Ordering::Less => self.entries[..base]
+                .iter()
+                .enumerate()
+                .rev()
+                .take_while(|(_, e)| e.path(self).eq_ignore_ascii_case(path))
+                .last()
+                .map(|(idx, _)| idx),
+        }
+    }
+
     fn entry_index_by_idx_and_stage(
         &self,
         path: &BStr,
@@ -133,6 +189,31 @@ impl State {
         }
     }
 
+    fn entry_index_by_idx_and_stage_icase(
+        &self,
+        path: &BStr,
+        idx: usize,
+        wanted_stage: entry::Stage,
+        stage_cmp: Ordering,
+    ) -> Option<usize> {
+        match stage_cmp {
+            Ordering::Greater => self.entries[..idx]
+                .iter()
+                .enumerate()
+                .rev()
+                .take_while(|(_, e)| e.path(self).eq_ignore_ascii_case(path))
+                .find_map(|(idx, e)| (e.stage() == wanted_stage).then_some(idx)),
+            Ordering::Equal => Some(idx),
+            Ordering::Less => self
+                .entries
+                .get(idx + 1..)?
+                .iter()
+                .enumerate()
+                .take_while(|(_, e)| e.path(self).eq_ignore_ascii_case(path))
+                .find_map(|(ofs, e)| (e.stage() == wanted_stage).then_some(idx + ofs + 1)),
+        }
+    }
+
     /// Find the entry index in [`entries()[..upper_bound]`][State::entries()] matching the given repository-relative
     /// `path` and `stage`, or `None`.
     ///
@@ -152,13 +233,89 @@ impl State {
             .ok()
     }
 
-    /// Like [`entry_index_by_path_and_stage()`][State::entry_index_by_path_and_stage()],
+    /// Like [`entry_index_by_path_and_stage()`](State::entry_index_by_path_and_stage_icase()),
     /// but returns the entry instead of the index.
     pub fn entry_by_path_and_stage(&self, path: &BStr, stage: entry::Stage) -> Option<&Entry> {
         self.entry_index_by_path_and_stage(path, stage)
             .map(|idx| &self.entries[idx])
     }
 
+    /// Like [`entry_index_by_path_and_stage_icase()`](State::entry_index_by_path_and_stage_icase()),
+    /// but returns the entry instead of the index.
+    pub fn entry_by_path_and_stage_icase(&self, path: &BStr, stage: entry::Stage, ignore_case: bool) -> Option<&Entry> {
+        self.entry_index_by_path_and_stage_icase(path, stage, ignore_case)
+            .map(|idx| &self.entries[idx])
+    }
+
+    /// Return the kind of directory that `path` represents, or `None` if the path is not a directory, or not
+    /// tracked in this index in any other way.
+    ///
+    /// Note that we will not match `path`, like `a/b`, to a submodule or sparse directory at `a`, which means
+    /// that `path` should be grown one component at a time in order to find the relevant entries.
+    ///
+    /// If `ignore_case` is `true`, a case-insensitive (ASCII-folding only) search will be performed.
+    ///
+    /// ### Deviation
+    ///
+    /// We allow conflicting entries to serve as indicator for an inferred directory, whereas `git` only looks
+    /// at stage 0.
+    pub fn directory_kind_by_path_icase(&self, path: &BStr, ignore_case: bool) -> Option<DirectoryKind> {
+        if ignore_case {
+            for entry in self
+                .prefixed_entries_range_icase(path, ignore_case)
+                .map(|range| &self.entries[range])?
+            {
+                let entry_path = entry.path(self);
+                if !entry_path.get(..path.len())?.eq_ignore_ascii_case(path) {
+                    // This can happen if the range starts with matches, then moves on to non-matches,
+                    // to finally and in matches again.
+                    // TODO(perf): start range from start to first mismatch, then continue from the end.
+                    continue;
+                }
+                match entry_path.get(path.len()) {
+                    Some(b'/') => {
+                        return Some(if entry.mode.is_sparse() {
+                            DirectoryKind::SparseDir
+                        } else {
+                            DirectoryKind::Inferred
+                        })
+                    }
+                    Some(_) => break,
+                    None => {
+                        if entry.mode.is_submodule() {
+                            return Some(DirectoryKind::Submodule);
+                        }
+                    }
+                }
+            }
+        } else {
+            let (Ok(idx) | Err(idx)) = self.entries.binary_search_by(|e| e.path(self).cmp(path));
+
+            for entry in self.entries.get(idx..)? {
+                let entry_path = entry.path(self);
+                if entry_path.get(..path.len())? != path {
+                    break;
+                }
+                match entry_path.get(path.len()) {
+                    Some(b'/') => {
+                        return Some(if entry.mode.is_sparse() {
+                            DirectoryKind::SparseDir
+                        } else {
+                            DirectoryKind::Inferred
+                        })
+                    }
+                    Some(_) => break,
+                    None => {
+                        if entry.mode.is_submodule() {
+                            return Some(DirectoryKind::Submodule);
+                        }
+                    }
+                }
+            }
+        }
+        None
+    }
+
     /// Return the entry at `path` that is either at stage 0, or at stage 2 (ours) in case of a merge conflict.
     ///
     /// Using this method is more efficient in comparison to doing two searches, one for stage 0 and one for stage 2.
@@ -182,6 +339,37 @@ impl State {
         Some(&self.entries[idx])
     }
 
+    /// Return the entry at `path` that is either at stage 0, or at stage 2 (ours) in case of a merge conflict.
+    /// If `ignore_case` is `true`, a case-insensitive (ASCII-folding only) search will be performed.
+    ///
+    /// Using this method is more efficient in comparison to doing two searches, one for stage 0 and one for stage 2.
+    ///
+    /// Note that if there are ambiguities, like `x` and `X` being present in the index, any of these will be returned,
+    /// deterministically.
+    pub fn entry_by_path_icase(&self, path: &BStr, ignore_case: bool) -> Option<&Entry> {
+        if ignore_case {
+            let mut stage_at_index = 0;
+            let idx = self
+                .entries
+                .binary_search_by(|e| {
+                    let res = icase_cmp(e.path(self), path);
+                    if res.is_eq() {
+                        stage_at_index = e.stage();
+                    }
+                    res
+                })
+                .ok()?;
+            let idx = if stage_at_index == 0 || stage_at_index == 2 {
+                idx
+            } else {
+                self.entry_index_by_idx_and_stage_icase(path, idx, 2, stage_at_index.cmp(&2))?
+            };
+            Some(&self.entries[idx])
+        } else {
+            self.entry_by_path(path)
+        }
+    }
+
     /// Return the slice of entries which all share the same `prefix`, or `None` if there isn't a single such entry.
     ///
     /// If `prefix` is empty, all entries are returned.
@@ -221,6 +409,49 @@ impl State {
         (low != high).then_some(low..high)
     }
 
+    /// Return the range of entries which all share the same `prefix`, or `None` if there isn't a single such entry.
+    /// If `ignore_case` is `true`, a case-insensitive (ASCII-folding only) search will be performed. Otherwise
+    /// the search is case-sensitive.
+    ///
+    /// If `prefix` is empty, the range will include all entries.
+    pub fn prefixed_entries_range_icase(&self, prefix: &BStr, ignore_case: bool) -> Option<Range<usize>> {
+        if ignore_case {
+            if prefix.is_empty() {
+                return Some(0..self.entries.len());
+            }
+            let prefix_len = prefix.len();
+            let mut low = self.entries.partition_point(|e| {
+                e.path(self).get(..prefix_len).map_or_else(
+                    || icase_cmp(e.path(self), &prefix[..e.path.len()]).is_le(),
+                    |p| icase_cmp(p, prefix).is_lt(),
+                )
+            });
+            let mut high = low
+                + self.entries[low..].partition_point(|e| {
+                    e.path(self)
+                        .get(..prefix_len)
+                        .map_or(false, |p| icase_cmp(p, prefix).is_le())
+                });
+
+            let low_entry = &self.entries.get(low)?;
+            if low_entry.stage() != 0 {
+                low = self
+                    .walk_entry_stages_icase(low_entry.path(self), low, Ordering::Less)
+                    .unwrap_or(low);
+            }
+            if let Some(high_entry) = self.entries.get(high) {
+                if high_entry.stage() != 0 {
+                    high = self
+                        .walk_entry_stages_icase(high_entry.path(self), high, Ordering::Less)
+                        .unwrap_or(high);
+                }
+            }
+            (low != high).then_some(low..high)
+        } else {
+            self.prefixed_entries_range(prefix)
+        }
+    }
+
     /// Return the entry at `idx` or _panic_ if the index is out of bounds.
     ///
     /// The `idx` is typically returned by [`entry_by_path_and_stage()`][State::entry_by_path_and_stage()].
@@ -260,6 +491,12 @@ impl State {
     }
 }
 
+fn icase_cmp(a: &[u8], b: &[u8]) -> Ordering {
+    a.iter()
+        .map(u8::to_ascii_lowercase)
+        .cmp(b.iter().map(u8::to_ascii_lowercase))
+}
+
 /// Mutation
 impl State {
     /// After usage of the storage obtained by [`take_path_backing()`][Self::take_path_backing()], return it here.

gix-index/src/lib.rs

@@ -47,6 +47,22 @@ pub enum Version {
     V4 = 4,
 }
 
+/// A representation of a directory in the index.
+///
+/// These are most of the time inferred, but may also be explicit entries.
+#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone, Copy)]
+pub enum DirectoryKind {
+    /// The directory is implied as there is at least one tracked entry that lives within it.
+    Inferred,
+    /// The directory is present directly in the form of a sparse directory.
+    ///
+    /// These are available when cone-mode is active.
+    SparseDir,
+    /// The directory is present directly in the form of the commit of a repository that is
+    /// a submodule of the superproject (which this is the index of).
+    Submodule,
+}
+
 /// An entry in the index, identifying a non-tree item on disk.
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct Entry {

gix-index/tests/fixtures/generated-archives/v2_deeper_tree.tar.xz

@@ -0,0 +1,28 @@
+#!/bin/bash
+set -eu -o pipefail
+
+export GIT_INDEX_VERSION=2;
+
+mkdir sub
+(cd sub
+  mkdir a b c
+  mkdir c/d
+  touch a/1 b/2 c/3 c/d/3
+)
+
+git init -q
+git config index.threads 1
+
+touch a b
+chmod +x b
+ln -s a c
+mkdir d
+(cd d && touch a b c
+  mkdir nested
+  (cd nested
+    touch 1
+  )
+)
+
+git add .
+git commit -m "init"

gix-index/tests/fixtures/generated-archives/v2_icase_name_clashes.tar.xz

@@ -0,0 +1,26 @@
+#!/bin/bash
+set -eu -o pipefail
+
+git init -q
+
+empty_oid=$(git hash-object -w --stdin </dev/null)
+content_oid=$(echo "content" | git hash-object -w --stdin)
+symlink_target=$(echo -n 'X' | git hash-object -w --stdin)
+
+echo "FILE_? filter=arrow" > .gitattributes
+git add -A
+
+git update-index --index-info <<-EOF
+100644 $content_oid	FILE_X
+100644 $content_oid	FILE_x
+100644 $content_oid	file_X
+100644 $content_oid	file_x
+100644 $empty_oid	D/B
+100644 $empty_oid	D/C
+100644 $empty_oid	d
+100644 $empty_oid	X
+120000 $symlink_target	x
+120000 $symlink_target	link-to-X
+EOF
+
+git commit -m "init"