Merge pull request desktop#17780 from desktop/what-about-these-images-now

Use merge base for deleted images in pull request preview

Author: tidy-dev

app/src/lib/git/diff.ts

@@ -8,6 +8,7 @@ import {
   FileChange,
   AppFileStatusKind,
   SubmoduleStatus,
+  CommittedFileChange,
 } from '../../models/status'
 import {
   DiffType,
@@ -433,7 +434,8 @@ async function getImageDiff(
     // File status can't be conflicted for a file in a commit
     if (
       file.status.kind !== AppFileStatusKind.New &&
-      file.status.kind !== AppFileStatusKind.Untracked
+      file.status.kind !== AppFileStatusKind.Untracked &&
+      file.status.kind !== AppFileStatusKind.Deleted
     ) {
       // TODO: commitish^ won't work for the first commit
       //
@@ -445,6 +447,17 @@ async function getImageDiff(
         `${oldestCommitish}^`
       )
     }
+
+    if (
+      file instanceof CommittedFileChange &&
+      file.status.kind === AppFileStatusKind.Deleted
+    ) {
+      previous = await getBlobImage(
+        repository,
+        getOldPathOrDefault(file),
+        file.parentCommitish
+      )
+    }
   }
 
   return {