feat!: add range to blame::file()

Author: cruessler

gix-blame/src/error.rs

@@ -27,4 +27,6 @@ pub enum Error {
     Traverse(#[source] Box<dyn std::error::Error + Send + Sync>),
     #[error(transparent)]
     DiffTree(#[from] gix_diff::tree::Error),
+    #[error("Invalid line range was given, line range is expected to be a 1-based inclusive range in the format '<start>,<end>'")]
+    InvalidLineRange,
 }

gix-blame/src/file/function.rs

@@ -25,6 +25,10 @@ use std::ops::Range;
 ///    - The first commit returned here is the first eligible commit to be responsible for parts of `file_path`.
 /// * `file_path`
 ///    - A *slash-separated* worktree-relative path to the file to blame.
+/// * `range`
+///    - A 1-based inclusive range, in order to mirror `git`’s behaviour. `Some(20..40)` represents
+///      21 lines, spanning from line 20 up to and including line 40. This will be converted to
+///      `19..40` internally as the algorithm uses 0-based ranges that are exclusive at the end.
 /// * `resource_cache`
 ///    - Used for diffing trees.
 ///
@@ -61,6 +65,7 @@ pub fn file<E>(
     traverse: impl IntoIterator<Item = Result<gix_traverse::commit::Info, E>>,
     resource_cache: &mut gix_diff::blob::Platform,
     file_path: &BStr,
+    range: Option<Range<u32>>,
 ) -> Result<Outcome, Error>
 where
     E: Into<Box<dyn std::error::Error + Send + Sync + 'static>>,
@@ -85,19 +90,37 @@ where
             .tokenize()
             .map(|token| interner.intern(token))
             .count()
-    };
+    } as u32;
 
     // Binary or otherwise empty?
     if num_lines_in_blamed == 0 {
         return Ok(Outcome::default());
     }
 
-    let mut hunks_to_blame = vec![{
-        let range_in_blamed_file = 0..num_lines_in_blamed as u32;
-        UnblamedHunk {
-            range_in_blamed_file: range_in_blamed_file.clone(),
-            suspects: [(suspect, range_in_blamed_file)].into(),
+    // This function assumes that `range` has 1-based inclusive line numbers and converts it to the
+    // format internally used: 0-based line numbers stored in ranges that are exclusive at the
+    // end.
+    let one_based_inclusive_to_zero_based_exclusive_range = || -> Result<Range<u32>, Error> {
+        if let Some(range) = range {
+            if range.start == 0 {
+                return Err(Error::InvalidLineRange);
+            }
+            let start = range.start - 1;
+            let end = range.end;
+            if start >= num_lines_in_blamed || end > num_lines_in_blamed || start == end {
+                return Err(Error::InvalidLineRange);
+            }
+            Ok(start..end)
+        } else {
+            Ok(0..num_lines_in_blamed)
         }
+    };
+
+    let range_in_blamed_file = one_based_inclusive_to_zero_based_exclusive_range()?;
+
+    let mut hunks_to_blame = vec![UnblamedHunk {
+        range_in_blamed_file: range_in_blamed_file.clone(),
+        suspects: [(suspect, range_in_blamed_file)].into(),
     }];
 
     let mut out = Vec::new();

gix-blame/tests/blame.rs

@@ -194,6 +194,7 @@ macro_rules! mktest {
                 commits,
                 &mut resource_cache,
                 format!("{}.txt", $case).as_str().into(),
+                None,
             )?
             .entries;
 
@@ -254,6 +255,7 @@ fn diff_disparity() {
             commits,
             &mut resource_cache,
             format!("{case}.txt").as_str().into(),
+            None,
         )
         .unwrap()
         .entries;
@@ -267,6 +269,26 @@ fn diff_disparity() {
     }
 }
 
+#[test]
+fn line_range() {
+    let Fixture {
+        odb,
+        mut resource_cache,
+        commits,
+    } = Fixture::new().unwrap();
+
+    let lines_blamed = gix_blame::file(&odb, commits, &mut resource_cache, "simple.txt".into(), Some(1..2))
+        .unwrap()
+        .entries;
+
+    assert_eq!(lines_blamed.len(), 2);
+
+    let git_dir = fixture_path().join(".git");
+    let baseline = Baseline::collect(git_dir.join("simple-lines-1-2.baseline")).unwrap();
+
+    assert_eq!(lines_blamed, baseline);
+}
+
 fn fixture_path() -> PathBuf {
     gix_testtools::scripted_fixture_read_only("make_blame_repo.sh").unwrap()
 }

gix-blame/tests/fixtures/make_blame_repo.sh

@@ -199,6 +199,7 @@ git commit -q -m c14.2
 git merge branch-that-has-one-of-the-changes || true
 
 git blame --porcelain simple.txt > .git/simple.baseline
+git blame --porcelain -L 1,2 simple.txt > .git/simple-lines-1-2.baseline
 git blame --porcelain multiline-hunks.txt > .git/multiline-hunks.baseline
 git blame --porcelain deleted-lines.txt > .git/deleted-lines.baseline
 git blame --porcelain deleted-lines-multiple-hunks.txt > .git/deleted-lines-multiple-hunks.baseline