feat: support configurable branch name for 'main' and other defaults

The branch name was hardcoded as 'master', causing the whitelist
feature to fail when repositories use 'main' or other default
branch names.

Changes:
- Add 'branch' parameter to page-attributes (defaults to 'master')
- Make branch variable in github.ts configurable via setRepoContext()
- Update error message link to use the configured branch

Fixes #523

Author: li5435945-ship-it

src/github.ts

@@ -15,11 +15,14 @@ export const reactionTypes: ReactionID[] = ['+1', '-1', 'laugh', 'hooray', 'conf
 
 let owner: string;
 let repo: string;
-const branch = 'master';
+let branch = 'master';
 
-export function setRepoContext(context: { owner: string; repo: string; }) {
+export function setRepoContext(context: { owner: string; repo: string; branch?: string; }) {
   owner = context.owner;
   repo = context.repo;
+  if (context.branch) {
+    branch = context.branch;
+  }
 }
 
 function githubRequest(relativeUrl: string, init?: RequestInit) {

src/page-attributes.ts

@@ -51,7 +51,8 @@ function readPageAttributes() {
     description: params.description,
     label: params.label,
     theme: params.theme || 'github-light',
-    session: params.session
+    session: params.session,
+    branch: params.branch || 'master'
   };
 }
 

src/utterances.ts

@@ -138,7 +138,7 @@ async function renderComments(issue: Issue, timeline: TimelineComponent) {
 
 export async function assertOrigin() {
   const { origins } = await getRepoConfig();
-  const { origin, owner, repo } = page;
+  const { origin, owner, repo, branch } = page;
   if (origins.indexOf(origin) !== -1) {
     return;
   }
@@ -147,7 +147,7 @@ export async function assertOrigin() {
   <div class="flash flash-error flash-not-installed">
     Error: <code>${origin}</code> is not permitted to post to <code>${owner}/${repo}</code>.
     Confirm this is the correct repo for this site's comments. If you own this repo,
-    <a href="https://github.com/${owner}/${repo}/edit/master/utterances.json" target="_top">
+    <a href="https://github.com/${owner}/${repo}/edit/${branch}/utterances.json" target="_top">
       <strong>update the utterances.json</strong>
     </a>
     to include <code>${origin}</code> in the list of origins.<br/><br/>