Show correct commits in PR diff (#20)

* Use parent commit as a base for showing PR diff

* update readme

README.md

@@ -12,15 +12,16 @@
 </p>
 
 
-|<img alt="Pull request order visible in pull requests" src="./.github/list-view.png" height="250px" /> | <img alt="Select parent pull request" src="./.github/parent-selector.png" height="250px" /> |
+|<img alt="Pull request order visible in pull requests" src="./.github/list-view.png" height="266px" /> | <img alt="Select parent pull request" src="./.github/parent-selector.png" height="266px" /> |
 |--|--|
 
 <p align="center">
-  <strong>View only changes made after the previous pull request</strong>
+  <strong>View only changes made in this pull request</strong>
 </p>
 
-|<img alt="Only relevant changes visible" src="./.github/only-relevant.png" height="200px" />|
+|<img alt="Only relevant changes visible" src="./.github/diff-all-visible.png" />|
 |--|
+|<img alt="Only relevant changes visible" src="./.github/diff-pr-visible.png" />|
 
 <p align="center">
   <strong>Automatic warnings on sequential pull requests</strong>

src/api.ts

@@ -43,6 +43,7 @@ export interface IGithubFork {
 }
 export interface IGithubCommit {
   sha: string;
+  parents: Array<{ sha: string }>;
 }
 
 async function makeRequest(

src/features/diff-select.tsx

@@ -48,7 +48,9 @@ function getDiffViewUrl(commits: IGithubCommit[]): string | null {
   } else if (commits.length > 1) {
     return (
       window.location.href +
-      `/${commits[0].sha}..${commits[commits.length - 1].sha}`
+      // TODO this is a too big of an assumption
+      // https://softwareengineering.stackexchange.com/questions/314215/can-a-git-commit-have-more-than-2-parents
+      `/${commits[0].parents[0].sha}..${commits[commits.length - 1].sha}`
     );
   } else {
     return null;
@@ -93,7 +95,7 @@ export default async function initialize(context: IStackerContext) {
         >
           Viewing all changes.{" "}
           <a className="stale-files-tab-link" href={diffViewUrl}>
-            🔎 View only this PR
+            🔎 &nbsp;View only this PR
           </a>
         </div>,
         $stats