feat!: follow renames in blame

Author: cruessler

gix-blame/src/error.rs

@@ -27,6 +27,8 @@ pub enum Error {
     Traverse(#[source] Box<dyn std::error::Error + Send + Sync>),
     #[error(transparent)]
     DiffTree(#[from] gix_diff::tree::Error),
+    #[error(transparent)]
+    DiffTreeWithRewrites(#[from] gix_diff::tree_with_rewrites::Error),
     #[error("Invalid line range was given, line range is expected to be a 1-based inclusive range in the format '<start>,<end>'")]
     InvalidLineRange,
     #[error("Failure to decode commit during traversal")]

gix-blame/src/file/function.rs

@@ -72,19 +72,21 @@ pub fn file(
 ) -> Result<Outcome, Error> {
     let _span = gix_trace::coarse!("gix_blame::file()", ?file_path, ?suspect);
 
+    let mut current_file_path: BString = file_path.into();
+
     let mut stats = Statistics::default();
     let (mut buf, mut buf2, mut buf3) = (Vec::new(), Vec::new(), Vec::new());
     let blamed_file_entry_id = find_path_entry_in_commit(
         &odb,
         &suspect,
-        file_path,
+        current_file_path.as_ref(),
         cache.as_ref(),
         &mut buf,
         &mut buf2,
         &mut stats,
     )?
     .ok_or_else(|| Error::FileMissing {
-        file_path: file_path.to_owned(),
+        file_path: current_file_path.to_owned(),
         commit_id: suspect,
     })?;
     let blamed_file_blob = odb.find_blob(&blamed_file_entry_id, &mut buf)?.data.to_vec();
@@ -102,6 +104,7 @@ pub fn file(
         hunks_to_blame.push(UnblamedHunk {
             range_in_blamed_file: range.clone(),
             suspects: [(suspect, range)].into(),
+            source_file_name: None,
         });
     }
 
@@ -165,7 +168,7 @@ pub fn file(
             entry = find_path_entry_in_commit(
                 &odb,
                 &suspect,
-                file_path,
+                current_file_path.as_ref(),
                 cache.as_ref(),
                 &mut buf,
                 &mut buf2,
@@ -216,7 +219,7 @@ pub fn file(
             if let Some(parent_entry_id) = find_path_entry_in_commit(
                 &odb,
                 parent_id,
-                file_path,
+                current_file_path.as_ref(),
                 cache.as_ref(),
                 &mut buf,
                 &mut buf2,
@@ -239,12 +242,13 @@ pub fn file(
             queue.insert(parent_commit_time, parent_id);
             let changes_for_file_path = tree_diff_at_file_path(
                 &odb,
-                file_path,
+                current_file_path.as_ref(),
                 suspect,
                 parent_id,
                 cache.as_ref(),
                 &mut stats,
                 &mut diff_state,
+                resource_cache,
                 &mut buf,
                 &mut buf2,
                 &mut buf3,
@@ -263,7 +267,7 @@ pub fn file(
             };
 
             match modification {
-                gix_diff::tree::recorder::Change::Addition { .. } => {
+                TreeDiffChange::Addition => {
                     if more_than_one_parent {
                         // Do nothing under the assumption that this always (or almost always)
                         // implies that the file comes from a different parent, compared to which
@@ -272,20 +276,44 @@ pub fn file(
                         break 'outer;
                     }
                 }
-                gix_diff::tree::recorder::Change::Deletion { .. } => {
+                TreeDiffChange::Deletion => {
                     unreachable!("We already found file_path in suspect^{{tree}}, so it can't be deleted")
                 }
-                gix_diff::tree::recorder::Change::Modification { previous_oid, oid, .. } => {
+                TreeDiffChange::Modification { previous_id, id } => {
                     let changes = blob_changes(
                         &odb,
                         resource_cache,
-                        oid,
-                        previous_oid,
-                        file_path,
+                        id,
+                        previous_id,
+                        current_file_path.as_ref(),
+                        options.diff_algorithm,
+                        &mut stats,
+                    )?;
+                    hunks_to_blame = process_changes(hunks_to_blame, changes, suspect, parent_id);
+                }
+                TreeDiffChange::Rewrite {
+                    source_location,
+                    source_id,
+                    id,
+                } => {
+                    let changes = blob_changes(
+                        &odb,
+                        resource_cache,
+                        id,
+                        source_id,
+                        current_file_path.as_ref(),
                         options.diff_algorithm,
                         &mut stats,
                     )?;
                     hunks_to_blame = process_changes(hunks_to_blame, changes, suspect, parent_id);
+
+                    for hunk in hunks_to_blame.iter_mut() {
+                        if hunk.has_suspect(&parent_id) {
+                            hunk.source_file_name = Some(source_location.clone());
+                        }
+                    }
+
+                    current_file_path = source_location;
                 }
             }
         }
@@ -382,6 +410,7 @@ fn coalesce_blame_entries(lines_blamed: Vec<BlameEntry>) -> Vec<BlameEntry> {
                         len: NonZeroU32::new((current_source_range.end - previous_source_range.start) as u32)
                             .expect("BUG: hunks are never zero-sized"),
                         commit_id: previous_entry.commit_id,
+                        source_file_name: previous_entry.source_file_name.clone(),
                     };
 
                     acc.pop();
@@ -399,6 +428,57 @@ fn coalesce_blame_entries(lines_blamed: Vec<BlameEntry>) -> Vec<BlameEntry> {
         })
 }
 
+enum TreeDiffChange {
+    Addition,
+    Deletion,
+    Modification {
+        previous_id: ObjectId,
+        id: ObjectId,
+    },
+    Rewrite {
+        source_location: BString,
+        source_id: ObjectId,
+        id: ObjectId,
+    },
+}
+
+impl From<gix_diff::tree::recorder::Change> for TreeDiffChange {
+    fn from(value: gix_diff::tree::recorder::Change) -> Self {
+        use gix_diff::tree::recorder::Change;
+
+        match value {
+            Change::Addition { .. } => Self::Addition,
+            Change::Deletion { .. } => Self::Deletion,
+            Change::Modification { previous_oid, oid, .. } => Self::Modification {
+                previous_id: previous_oid,
+                id: oid,
+            },
+        }
+    }
+}
+
+impl From<gix_diff::tree_with_rewrites::Change> for TreeDiffChange {
+    fn from(value: gix_diff::tree_with_rewrites::Change) -> Self {
+        use gix_diff::tree_with_rewrites::Change;
+
+        match value {
+            Change::Addition { .. } => Self::Addition,
+            Change::Deletion { .. } => Self::Deletion,
+            Change::Modification { previous_id, id, .. } => Self::Modification { previous_id, id },
+            Change::Rewrite {
+                source_location,
+                source_id,
+                id,
+                ..
+            } => Self::Rewrite {
+                source_location,
+                source_id,
+                id,
+            },
+        }
+    }
+}
+
 #[allow(clippy::too_many_arguments)]
 fn tree_diff_at_file_path(
     odb: impl gix_object::Find + gix_object::FindHeader,
@@ -408,10 +488,11 @@ fn tree_diff_at_file_path(
     cache: Option<&gix_commitgraph::Graph>,
     stats: &mut Statistics,
     state: &mut gix_diff::tree::State,
+    resource_cache: &mut gix_diff::blob::Platform,
     commit_buf: &mut Vec<u8>,
     lhs_tree_buf: &mut Vec<u8>,
     rhs_tree_buf: &mut Vec<u8>,
-) -> Result<Option<gix_diff::tree::recorder::Change>, Error> {
+) -> Result<Option<TreeDiffChange>, Error> {
     let parent_tree_id = find_commit(cache, &odb, &parent_id, commit_buf)?.tree_id()?;
 
     let parent_tree_iter = odb.find_tree_iter(&parent_tree_id, lhs_tree_buf)?;
@@ -422,6 +503,37 @@ fn tree_diff_at_file_path(
     let tree_iter = odb.find_tree_iter(&tree_id, rhs_tree_buf)?;
     stats.trees_decoded += 1;
 
+    let result = tree_diff_without_rewrites_at_file_path(&odb, file_path, stats, state, parent_tree_iter, tree_iter)?;
+
+    // Here, we follow git’s behaviour. We return when we’ve found a `Modification`. We try a
+    // second time with rename tracking when the change is either an `Addition` or a `Deletion`
+    // because those can turn out to have been a `Rewrite`.
+    if matches!(result, Some(TreeDiffChange::Modification { .. })) {
+        return Ok(result);
+    }
+
+    let result = tree_diff_with_rewrites_at_file_path(
+        &odb,
+        file_path,
+        stats,
+        state,
+        resource_cache,
+        parent_tree_iter,
+        tree_iter,
+    )?;
+
+    Ok(result)
+}
+
+#[allow(clippy::too_many_arguments)]
+fn tree_diff_without_rewrites_at_file_path(
+    odb: impl gix_object::Find + gix_object::FindHeader,
+    file_path: &BStr,
+    stats: &mut Statistics,
+    state: &mut gix_diff::tree::State,
+    parent_tree_iter: gix_object::TreeRefIter<'_>,
+    tree_iter: gix_object::TreeRefIter<'_>,
+) -> Result<Option<TreeDiffChange>, Error> {
     struct FindChangeToPath {
         inner: gix_diff::tree::Recorder,
         interesting_path: BString,
@@ -509,11 +621,53 @@ fn tree_diff_at_file_path(
     stats.trees_diffed += 1;
 
     match result {
-        Ok(_) | Err(gix_diff::tree::Error::Cancelled) => Ok(recorder.change),
+        Ok(_) | Err(gix_diff::tree::Error::Cancelled) => Ok(recorder.change.map(std::convert::Into::into)),
         Err(error) => Err(Error::DiffTree(error)),
     }
 }
 
+#[allow(clippy::too_many_arguments)]
+fn tree_diff_with_rewrites_at_file_path(
+    odb: impl gix_object::Find + gix_object::FindHeader,
+    file_path: &BStr,
+    stats: &mut Statistics,
+    state: &mut gix_diff::tree::State,
+    resource_cache: &mut gix_diff::blob::Platform,
+    parent_tree_iter: gix_object::TreeRefIter<'_>,
+    tree_iter: gix_object::TreeRefIter<'_>,
+) -> Result<Option<TreeDiffChange>, Error> {
+    let mut change: Option<gix_diff::tree_with_rewrites::Change> = None;
+
+    let options: gix_diff::tree_with_rewrites::Options = gix_diff::tree_with_rewrites::Options {
+        location: Some(gix_diff::tree::recorder::Location::Path),
+        rewrites: Some(gix_diff::Rewrites::default()),
+    };
+    let result = gix_diff::tree_with_rewrites(
+        parent_tree_iter,
+        tree_iter,
+        resource_cache,
+        state,
+        &odb,
+        |change_ref| -> Result<_, std::convert::Infallible> {
+            if change_ref.location() == file_path {
+                change = Some(change_ref.into_owned());
+                Ok(gix_diff::tree_with_rewrites::Action::Cancel)
+            } else {
+                Ok(gix_diff::tree_with_rewrites::Action::Continue)
+            }
+        },
+        options,
+    );
+    stats.trees_diffed_with_rewrites += 1;
+
+    match result {
+        Ok(_) | Err(gix_diff::tree_with_rewrites::Error::Diff(gix_diff::tree::Error::Cancelled)) => {
+            Ok(change.map(std::convert::Into::into))
+        }
+        Err(error) => Err(Error::DiffTreeWithRewrites(error)),
+    }
+}
+
 fn blob_changes(
     odb: impl gix_object::Find + gix_object::FindHeader,
     resource_cache: &mut gix_diff::blob::Platform,

gix-blame/src/file/mod.rs

@@ -393,11 +393,13 @@ impl UnblamedHunk {
                         range_in_blamed_file: self.range_in_blamed_file.start
                             ..(self.range_in_blamed_file.start + split_at_from_start),
                         suspects: new_suspects_before.collect(),
+                        source_file_name: self.source_file_name.clone(),
                     };
                     let new_hunk_after = Self {
                         range_in_blamed_file: (self.range_in_blamed_file.start + split_at_from_start)
                             ..(self.range_in_blamed_file.end),
                         suspects: new_suspects_after.collect(),
+                        source_file_name: self.source_file_name,
                     };
 
                     Either::Right((new_hunk_before, new_hunk_after))
@@ -445,6 +447,7 @@ impl BlameEntry {
             start_in_source_file: range_in_source_file.start,
             len: force_non_zero(range_in_source_file.len() as u32),
             commit_id,
+            source_file_name: unblamed_hunk.source_file_name.clone(),
         })
     }
 }