feat: add local diff review workflow

src/repository.rs

@@ -1058,6 +1058,7 @@ struct PreparedComparison {
     id: u64,
     selected: [Revision; 2],
     selected_ids: [Option<String>; 2],
+    revisions: [String; 2],
     mode: ComparisonMode,
     left: Snapshot,
     right: Snapshot,
@@ -2284,6 +2285,34 @@ impl Repository {
         }
         Ok(snapshot)
     }
+    fn snapshot_revision(
+        &mut self,
+        target: &RevisionTarget,
+        snapshot: &Snapshot,
+    ) -> Result<String, String> {
+        if let RevisionTarget::Commit(id) = target {
+            return Ok(id.clone());
+        }
+        self.ensure_private()?;
+        let store = &self.private.as_ref().unwrap().1;
+        let mut input = b"vamp-working-snapshot-v1\0".to_vec();
+        for (path, file) in snapshot {
+            self.check_cancelled()?;
+            for field in [
+                path.as_os_str().as_encoded_bytes(),
+                file.mode.as_bytes(),
+                file.bytes.as_slice(),
+                file.notice.as_deref().unwrap_or("").as_bytes(),
+            ] {
+                input.extend_from_slice(&(field.len() as u64).to_be_bytes());
+                input.extend_from_slice(field);
+            }
+        }
+        let mut command = git_command(store);
+        command.args(["hash-object", "--no-filters", "--stdin"]);
+        let id = text(checked(run(command, input, &self.cancelled)?)?)?;
+        Ok(format!("working:{}", id.trim()))
+    }
     fn snapshot(&mut self, target: &RevisionTarget) -> Result<Snapshot, String> {
         if *target == RevisionTarget::Working {
             self.working_snapshot(&[])
@@ -2454,10 +2483,17 @@ impl Repository {
             let (store, id) = pinned.as_ref().unwrap();
             self.commit_snapshot(store, id)?
         };
+        let before_revision = self.snapshot_revision(before_target, &left)?;
+        let after_revision = if same {
+            before_revision.clone()
+        } else {
+            self.snapshot_revision(after_target, &right)?
+        };
         let mut prepared = PreparedComparison {
             id: comparison_id,
             selected: [before.clone(), after.clone()],
             selected_ids,
+            revisions: [before_revision, after_revision],
             mode,
             left,
             right,
@@ -2574,9 +2610,11 @@ impl Repository {
             return Ok(None);
         }
         let right = self.working_snapshot(buffers)?;
+        let revision = self.snapshot_revision(&RevisionTarget::Working, &right)?;
         let mut prepared = self.comparison.take().unwrap();
         let previous_right = std::mem::replace(&mut prepared.right, right);
         let previous_files = std::mem::take(&mut prepared.files);
+        let previous_revision = std::mem::replace(&mut prepared.revisions[1], revision);
         let result = self
             .build_comparison(&mut prepared, false)
             .and_then(|comparison| {
@@ -2598,6 +2636,7 @@ impl Repository {
         } else {
             prepared.right = previous_right;
             prepared.files = previous_files;
+            prepared.revisions[1] = previous_revision;
         }
         self.comparison = Some(prepared);
         result.map(|comparison| Some(CheckoutRefresh::Checkout(comparison)))
@@ -2628,11 +2667,14 @@ impl Repository {
         let advance_working = working_after
             && follow_working
             && self.working_advanced(prepared.working_anchor.as_deref(), anchor.as_deref())?;
+        let mut revisions = prepared.revisions.clone();
         let (left, before_label) = if branch {
             let base = self.merge_base(ids[0].as_deref().unwrap(), ids[1].as_deref().unwrap())?;
             let label = format!("merge base of {label} and {after_label} · {base}");
+            revisions[0] = base.clone();
             (Some(self.snapshot(&RevisionTarget::Commit(base))?), label)
         } else if changed_before {
+            revisions[0] = ids[0].clone().unwrap();
             (
                 Some(self.snapshot(&RevisionTarget::Commit(ids[0].clone().unwrap()))?),
                 label,
@@ -2647,6 +2689,13 @@ impl Repository {
         } else {
             None
         };
+        if let Some(right) = &right {
+            revisions[1] = if advance_working {
+                self.snapshot_revision(&RevisionTarget::Working, right)?
+            } else {
+                ids[1].clone().unwrap()
+            };
+        }
         let pinned_checkout = ids[1]
             .as_deref()
             .map(|id| self.pinned_checkout(id))
@@ -2658,6 +2707,7 @@ impl Repository {
         let previous_files = std::mem::take(&mut prepared.files);
         let previous_before = std::mem::replace(&mut prepared.before, before_label);
         let previous_editable = prepared.editable_after;
+        let previous_revisions = std::mem::replace(&mut prepared.revisions, revisions);
         prepared.editable_after =
             working_after || (pinned_checkout.is_some() && pinned_checkout == anchor);
         let result = self
@@ -2693,6 +2743,7 @@ impl Repository {
             prepared.files = previous_files;
             prepared.before = previous_before;
             prepared.editable_after = previous_editable;
+            prepared.revisions = previous_revisions;
         }
         self.comparison = Some(prepared);
         result
@@ -2810,6 +2861,7 @@ impl Repository {
             BTreeSet::new()
         };
         Comparison {
+            revisions: prepared.revisions.clone(),
             before: prepared.before.clone(),
             after: prepared.after.clone(),
             files,