fix(gix-index): correctly decode untracked extension

gix-index/Cargo.toml

@@ -76,6 +76,7 @@ gix-hashtable = { path = "../gix-hashtable" }
 gix-odb = { path = "../gix-odb" }
 gix-object = { path = "../gix-object" }
 filetime = "0.2.27"
+insta = { version = "1.46.3", features = ["filters"] }
 
 [package.metadata.docs.rs]
 features = ["sha1", "document-features", "serde"]

gix-index/src/decode/mod.rs

@@ -336,11 +336,11 @@ pub(crate) fn stat(data: &[u8]) -> Option<(entry::Stat, &[u8])> {
     let (size, data) = read_u32(data)?;
     Some((
         entry::Stat {
-            mtime: entry::stat::Time {
+            ctime: entry::stat::Time {
                 secs: ctime_secs,
                 nsecs: ctime_nsecs,
             },
-            ctime: entry::stat::Time {
+            mtime: entry::stat::Time {
                 secs: mtime_secs,
                 nsecs: mtime_nsecs,
             },

gix-index/src/extension/mod.rs

@@ -45,7 +45,7 @@ pub struct Link {
 
 /// The extension for untracked files.
 #[allow(dead_code)]
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct UntrackedCache {
     /// Something identifying the location and machine that this cache is for.
     /// Should the repository be copied to a different machine, the entire cache can immediately be invalidated.

gix-index/src/extension/untracked_cache.rs

@@ -7,17 +7,61 @@ use crate::{
     util::{read_u32, split_at_byte_exclusive, var_int},
 };
 
+impl UntrackedCache {
+    /// Something identifying the location and machine that this cache is for.
+    pub fn identifier(&self) -> &bstr::BStr {
+        self.identifier.as_ref()
+    }
+
+    /// Stat and object id for the `.git/info/exclude` file, if available.
+    pub fn info_exclude(&self) -> Option<&OidStat> {
+        self.info_exclude.as_ref()
+    }
+
+    /// Stat and object id for the `core.excludesfile`, if available.
+    pub fn excludes_file(&self) -> Option<&OidStat> {
+        self.excludes_file.as_ref()
+    }
+
+    /// Usually `.gitignore`.
+    pub fn exclude_filename_per_dir(&self) -> &bstr::BStr {
+        self.exclude_filename_per_dir.as_ref()
+    }
+
+    /// The directory flags Git used while populating the cache.
+    pub fn dir_flags(&self) -> u32 {
+        self.dir_flags
+    }
+
+    /// A list of directories and sub-directories, with `directories[0]` being the root.
+    pub fn directories(&self) -> &[Directory] {
+        &self.directories
+    }
+}
+
 /// A structure to track filesystem stat information along with an object id, linking a worktree file with what's in our ODB.
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct OidStat {
     /// The file system stat information
     pub stat: entry::Stat,
     /// The id of the file in our ODB.
     pub id: ObjectId,
 }
 
+impl OidStat {
+    /// The file system stat information.
+    pub fn stat(&self) -> &entry::Stat {
+        &self.stat
+    }
+
+    /// The id of the file in our ODB.
+    pub fn id(&self) -> ObjectId {
+        self.id
+    }
+}
+
 /// A directory with information about its untracked files, and its sub-directories
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct Directory {
     /// The directories name, or an empty string if this is the root directory.
     pub name: BString,
@@ -34,10 +78,42 @@ pub struct Directory {
     pub check_only: bool,
 }
 
+impl Directory {
+    /// The directory name, or an empty string if this is the root directory.
+    /// `/` is always used as path-separator.
+    pub fn name(&self) -> &bstr::BStr {
+        self.name.as_ref()
+    }
+
+    /// Untracked files and directory names.
+    pub fn untracked_entries(&self) -> &[BString] {
+        &self.untracked_entries
+    }
+
+    /// Indices for sub-directories similar to this one.
+    pub fn sub_directories(&self) -> &[usize] {
+        &self.sub_directories
+    }
+
+    /// The directory stat data, if available and valid.
+    pub fn stat(&self) -> Option<&entry::Stat> {
+        self.stat.as_ref()
+    }
+
+    /// The oid of a `.gitignore` file, if it exists.
+    pub fn exclude_file_oid(&self) -> Option<ObjectId> {
+        self.exclude_file_oid
+    }
+
+    /// Whether Git marked this directory as check-only.
+    pub fn check_only(&self) -> bool {
+        self.check_only
+    }
+}
+
 /// Only used as an indicator
 pub const SIGNATURE: Signature = *b"UNTR";
 
-// #[allow(unused)]
 /// Decode an untracked cache extension from `data`, assuming object hashes are of type `object_hash`.
 pub fn decode(data: &[u8], object_hash: gix_hash::Kind, alloc_limit_bytes: Option<usize>) -> Option<UntrackedCache> {
     if data.last().is_none_or(|b| *b != 0) {
@@ -46,10 +122,29 @@ pub fn decode(data: &[u8], object_hash: gix_hash::Kind, alloc_limit_bytes: Optio
     let (identifier_len, data) = var_int(data)?;
     let (identifier, data) = data.split_at_checked(identifier_len.try_into().ok()?)?;
 
+    // The on-disk layout matches git's `ondisk_untracked_cache` struct
+    // https://github.com/git/git/blob/2855562ca6a9c6b0e7bc780b050c1e83c9fcfbd0/dir.c#L3582-L3586
+    // https://github.com/git/git/blob/2855562ca6a9c6b0e7bc780b050c1e83c9fcfbd0/dir.c#L3668-L3722
+    //   info_exclude_stat  (36 bytes)
+    //   excludes_file_stat (36 bytes)
+    //   dir_flags          ( 4 bytes)
+    //   info_exclude hash  (hash_len bytes)
+    //   excludes_file hash (hash_len bytes)
+    //   exclude_per_dir    (NUL-terminated)
     let hash_len = object_hash.len_in_bytes();
-    let (info_exclude, data) = decode_oid_stat(data, hash_len)?;
-    let (excludes_file, data) = decode_oid_stat(data, hash_len)?;
+    let (info_exclude_stat, data) = crate::decode::stat(data)?;
+    let (excludes_file_stat, data) = crate::decode::stat(data)?;
     let (dir_flags, data) = read_u32(data)?;
+    let (info_exclude_hash, data) = data.split_at_checked(hash_len)?;
+    let (excludes_file_hash, data) = data.split_at_checked(hash_len)?;
+    let info_exclude = OidStat {
+        stat: info_exclude_stat,
+        id: ObjectId::from_bytes_or_panic(info_exclude_hash),
+    };
+    let excludes_file = OidStat {
+        stat: excludes_file_stat,
+        id: ObjectId::from_bytes_or_panic(excludes_file_hash),
+    };
     let (exclude_filename_per_dir, data) = split_at_byte_exclusive(data, 0)?;
 
     let (num_directory_blocks, data) = var_int(data)?;
@@ -174,15 +269,3 @@ fn decode_directory_block<'a>(
 
     data.into()
 }
-
-fn decode_oid_stat(data: &[u8], hash_len: usize) -> Option<(OidStat, &[u8])> {
-    let (stat, data) = crate::decode::stat(data)?;
-    let (hash, data) = data.split_at_checked(hash_len)?;
-    Some((
-        OidStat {
-            stat,
-            id: ObjectId::from_bytes_or_panic(hash),
-        },
-        data,
-    ))
-}

gix-index/tests/fixtures/make_index/untracked_cache_empty.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -eu -o pipefail
+
+git init -q
+
+mkdir tracked-dir untracked-dir-2 untracked-dir-3
+touch tracked-root-one tracked-root-two untracked-root-file \
+    tracked-dir/tracked-file \
+    untracked-dir-2/untracked-file-two \
+    untracked-dir-3/untracked-file-three
+git add tracked-root-one tracked-root-two tracked-dir/tracked-file
+: >.git/info/exclude
+git update-index --untracked-cache

gix-index/tests/fixtures/make_index/untracked_cache_nested.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+set -eu -o pipefail
+
+GIT_FORCE_UNTRACKED_CACHE=true
+export GIT_FORCE_UNTRACKED_CACHE
+
+git init -q
+git config core.excludesFile ""
+
+# This fixture extends the populated case with a tracked per-directory
+# `.gitignore` and nested untracked directories. The path names are intentionally
+# verbose because the test snapshots assert the decoded UNTR directory graph.
+mkdir -p tracked-dir-with-ignore/nested-untracked-dir/deep-untracked-dir \
+    untracked-dir-2 \
+    untracked-dir-3
+touch tracked-root-one tracked-root-two untracked-root-file \
+    tracked-dir-with-ignore/tracked-file \
+    tracked-dir-with-ignore/visible-untracked-file \
+    tracked-dir-with-ignore/nested-untracked-dir/deep-untracked-dir/deep-untracked-file \
+    untracked-dir-2/untracked-file-two \
+    untracked-dir-3/untracked-file-three
+printf "ignored-by-dir-ignore\nalso-ignored-by-dir-ignore\n" >tracked-dir-with-ignore/.gitignore
+git add tracked-root-one tracked-root-two tracked-dir-with-ignore/tracked-file tracked-dir-with-ignore/.gitignore
+mkdir -p .git/info
+: >.git/info/exclude
+git update-index --untracked-cache
+git status --porcelain >/dev/null

gix-index/tests/fixtures/make_index/untracked_cache_populated.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -eu -o pipefail
+
+# Reuse the empty UNTR fixture and run status so Git fills the cache with the
+# descriptive tracked/untracked path layout from that script.
+. "$(dirname -- "${BASH_SOURCE[0]}")/untracked_cache_empty.sh"
+# This triggers the untracked cache to be refreshed.
+git status > /dev/null