build: [12.x] preparation for primary branch rename in the Angular repos (#24791)

Preparation for the components repo as outlined our planning
document.

Author: devversion

.circleci/config.yml

@@ -82,6 +82,8 @@ var_13: &attach_release_output
 var_14: &publish_branches_filter
   branches:
     only:
+      - main
+      # TODO(BRANCH_RENAME_CLEANUP): remove
       - master
       # 6.0.x, 7.1.x, etc.
       - /\d+\.\d+\.x/
@@ -134,8 +136,10 @@ var_20: &slack_notify_on_failure
 # Branch filter that only matches the main branch.
 var_21: &only_main_branch_filter
   branches:
-      only:
-        - master
+    only:
+      - main
+        # TODO(BRANCH_RENAME_CLEANUP): remove
+      - master
 
 # -----------------------------
 # Container version of CircleCI
@@ -715,7 +719,9 @@ workflows:
           filters:
             branches:
               only:
-                # We only want to run the "master" branch against the snapshot builds because
+                # We only want to run the main branch against the snapshot builds because
                 # it's not guaranteed that older versions of Angular Material always work
                 # with the latest Angular version.
+                - main
+                # TODO(BRANCH_RENAME_CLEANUP): remove
                 - master

.circleci/rebase-pr.js

@@ -95,22 +95,31 @@ async function _main() {
 /**
  * Sort a list of fullpath refs into a list and then provide the first entry.
  *
- * The sort order will first find master ref, and then any semver ref, followed
+ * The sort order will first find main branch, and then any semver ref, followed
  * by the rest of the refs in the order provided.
  *
- * Branches are sorted in this order as work is primarily done on master, and
- * otherwise on a semver branch. If neither of those were to match, the most
+ * Branches are sorted in this order as work is primarily done on main branches,
+ * and otherwise on a semver branch. If neither of those were to match, the most
  * likely correct branch will be the first one encountered in the list.
  */
 function getRefFromBranchList(gitOutput) {
   const branches = gitOutput.split('\n').map(b => b.split('/').slice(1).join('').trim());
   return branches.sort((a, b) => {
+    if (a === 'main') {
+      return -1;
+    }
+    if (b === 'main') {
+      return 1;
+    }
+
+    // TODO(BRANCH_RENAME_CLEANUP): remove
     if (a === 'master') {
       return -1;
     }
     if (b === 'master') {
       return 1;
     }
+
     const aIsSemver = semverRegex.test(a);
     const bIsSemver = semverRegex.test(b);
     if (aIsSemver && bIsSemver) {