Merge pull request #125 from triblespace/codex/update-commit-selector-to-use-set-operations

Improve two-dot commit range semantics

Author: somethingelseentirely

CHANGELOG.md

@@ -149,6 +149,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Introduced an `ancestors` selector to retrieve a commit and its history.
 - Commit selectors now return a `CommitSet` patch of commit handles instead of a `Vec`.
 - Renamed the `CommitPatch` type alias to `CommitSet`.
+- The `..` commit selector now computes `reachable(end) minus reachable(start)`
+  via set operations, matching Git's two-dot semantics even across merges.
 
 ## [0.5.2] - 2025-06-30
 ### Added

src/repo.rs

@@ -938,10 +938,9 @@ where
         CommitSet,
         WorkspaceCheckoutError<<Blobs::Reader as BlobStoreGet<Blake3>>::GetError<UnarchiveError>>,
     > {
-        let mut patch = collect_range(ws, Some(self.start), Some(self.end), true)?;
-        // Exclude the starting commit to mirror git semantics
-        patch.remove(&self.start.raw);
-        Ok(patch)
+        let patch = collect_reachable(ws, self.end)?;
+        let exclude = collect_reachable(ws, self.start)?;
+        Ok(patch.difference(&exclude))
     }
 }