Add a test combining renames and edits on multiple branches (#2366)

* Add a test combining renames and edits on multiple branches

* Regenerate `make_blame_rename_tracking_repo` archive

Done by running

    gix clean -xde
    cargo nextest run --workspace --no-fail-fast

on an Ubuntu 25.10 system, and verifying that all tests passed and
that exactly one non-`.gitignore`'d archive was regenerated.

* Unify diff style, with changes indicated by `number written out` instead of `number`

This style is used in `gix-diff` already, and I think it's minimal and easy to understand.

---------

Co-authored-by: Eliah Kagan <degeneracypressure@gmail.com>
Co-authored-by: Sebastian Thiel <sebastian.thiel@icloud.com>

Author: 3 people

gix-blame/tests/blame.rs

@@ -207,6 +207,21 @@ impl Fixture {
             suspect: head_id,
         })
     }
+
+    fn blame_file(
+        &mut self,
+        source_file_name: &bstr::BStr,
+        options: gix_blame::Options,
+    ) -> Result<gix_blame::Outcome, gix_blame::Error> {
+        gix_blame::file(
+            &self.odb,
+            self.suspect,
+            None,
+            &mut self.resource_cache,
+            source_file_name,
+            options,
+        )
+    }
 }
 
 macro_rules! mktest {
@@ -584,6 +599,36 @@ mod rename_tracking {
 
         Ok(())
     }
+
+    #[test]
+    fn rename_and_change_in_merge_commit() -> gix_testtools::Result {
+        let worktree_path = gix_testtools::scripted_fixture_read_only("make_blame_rename_tracking_repo.sh")?;
+
+        let mut fixture = Fixture::for_worktree_path(worktree_path.to_path_buf())?;
+        let source_file_name = "change-and-renamed.txt";
+
+        let lines_blamed = fixture
+            .blame_file(
+                source_file_name.into(),
+                gix_blame::Options {
+                    diff_algorithm: gix_diff::blob::Algorithm::Histogram,
+                    ranges: BlameRanges::default(),
+                    since: None,
+                    rewrites: Some(gix_diff::Rewrites::default()),
+                    debug_track_path: false,
+                },
+            )?
+            .entries;
+
+        assert_eq!(lines_blamed.len(), 4);
+
+        let git_dir = worktree_path.join(".git");
+        let baseline = Baseline::collect(git_dir.join("change-and-renamed.baseline"), source_file_name.into())?;
+
+        pretty_assertions::assert_eq!(lines_blamed, baseline);
+
+        Ok(())
+    }
 }
 
 fn fixture_path() -> gix_testtools::Result<PathBuf> {

gix-blame/tests/fixtures/generated-archives/make_blame_rename_tracking_repo.tar

@@ -35,3 +35,33 @@ git checkout main
 git merge different-branch || true
 
 git blame --porcelain after-rename.txt > .git/after-rename.baseline
+
+echo -e "1\n2\n3\n4\n5\n" > change-and-rename.txt
+git add change-and-rename.txt
+git commit -q -m c2.1.1
+
+echo -e "1\ntwo\n3\n4\n5\n" > change-and-rename.txt
+git add change-and-rename.txt
+git commit -q -m c2.1.2
+
+git checkout -b branch-that-renames-file
+git reset --hard HEAD~1
+
+echo -e "1\n2\n3\nfour\n5\n" > change-and-rename.txt
+git add change-and-rename.txt
+git commit -q -m c2.2.1
+
+mv change-and-rename.txt change-and-renamed.txt
+git add change-and-rename.txt change-and-renamed.txt
+git commit -q -m c2.2.2
+
+echo -e "1\n2\n3\nfour\nfive\n" > change-and-renamed.txt
+git add change-and-renamed.txt
+git commit -q -m c2.2.2
+
+git checkout main
+git merge branch-that-renames-file || true
+git add change-and-rename.txt
+git commit --no-edit
+
+git blame --porcelain change-and-renamed.txt > .git/change-and-renamed.baseline