[builder] Switch branch references to main

Fixes: b/260321001
Change-Id: I9716443cd0ba2eff415848a977d3601d2d058405
Reviewed-on: https://dart-review.googlesource.com/c/dart_ci/+/271980
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Auto-Submit: Alexander Thomas <athom@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>
diff --git a/builder/lib/src/commits_cache.dart b/builder/lib/src/commits_cache.dart
index 950400b..1a5b742 100644
--- a/builder/lib/src/commits_cache.dart
+++ b/builder/lib/src/commits_cache.dart
@@ -69,7 +69,7 @@
     final lastHash = lastCommit.hash;
     final lastIndex = lastCommit.index;
 
-    final branch = 'master';
+    final branch = 'main';
     final logUrl = 'https://dart.googlesource.com/sdk/+log/';
     final range = '$lastHash..$branch';
     final parameters = ['format=JSON', 'topo-order', 'first-parent', 'n=1000'];
diff --git a/builder/test/gerrit_review_json.dart b/builder/test/gerrit_review_json.dart
index 2da5c32..48d2c9a 100644
--- a/builder/test/gerrit_review_json.dart
+++ b/builder/test/gerrit_review_json.dart
@@ -6,9 +6,9 @@
 // with emails and names removed.
 String revertReviewGerritLog = r'''
 {
-  "id": "sdk~master~Ie212fae88bc1977e34e4d791c644b77783a8deb1",
+  "id": "sdk~main~Ie212fae88bc1977e34e4d791c644b77783a8deb1",
   "project": "sdk",
-  "branch": "master",
+  "branch": "main",
   "hashtags": [],
   "change_id": "Ie212fae88bc1977e34e4d791c644b77783a8deb1",
   "subject": "Revert \"[SDK] Adds IndirectGoto implementation of sync-yield.\"",