Fix main branch name in various CI tasks (#6063)

Author: emilypgoogle

.github/workflows/ci_tests.yml

@@ -6,7 +6,7 @@ on:
   pull_request:
   push:
     branches:
-      - master
+      - main
 
 jobs:
   determine_changed:

.github/workflows/diff-javadoc.yml

@@ -31,18 +31,18 @@ jobs:
       - name: Move branch docs to diff directory
         run: mv build ~/diff/modified
 
-      - name: Checkout master
+      - name: Checkout main
         uses: actions/checkout@v4.1.1
         with:
           ref: ${{ github.base_ref }}
 
-      - name: Generate docs for Master
+      - name: Generate docs for main
         run: ./gradlew kotlindoc
 
-      - name: Move master docs to diff directory
+      - name: Move main docs to diff directory
         run: mv build ~/diff/original
 
-      - name: Get diff between Master and Branch docs
+      - name: Get diff between main and Branch docs
         run: >
           `# Recursively diff directories, including new files, git style, with 3 lines of context`
           diff -wEburN ~/diff/original ~/diff/modified

.github/workflows/health-metrics.yml

@@ -8,7 +8,7 @@ on:
   pull_request:
   push:
     branches:
-      - master
+      - main
       # add other feature branches here
   # TODO(yifany): support workflow_dispatch for metric tests (or only for startup time test)
 
@@ -92,7 +92,7 @@ jobs:
       (github.event_name == 'push' && github.repository == 'firebase/firebase-android-sdk')
         || (github.event_name == 'pull_request'
               && github.event.pull_request.head.repo.full_name == github.repository
-              && github.event.pull_request.base.ref == 'master')
+              && github.event.pull_request.base.ref == 'main')
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4.1.1

.github/workflows/jekyll-gh-pages.yml

@@ -3,7 +3,7 @@ name: Jekyll with GitHub Pages
 on:
   # Runs on pushes targeting the default branch
   push:
-    branches: ["master"]
+    branches: ["main"]
     paths:
       - '.github/workflows/jekyll-gh-pages.yml'
       - 'contributor-docs/**'

.github/workflows/merge-to-main.yml

@@ -3,7 +3,7 @@ name: Merge to main
 on:
   pull_request:
     branches:
-      - master
+      - main
     types:
       - opened
       - labeled

.github/workflows/post_release_cleanup.yml

@@ -28,7 +28,7 @@ jobs:
       - name: Create Pull Request
         uses: peter-evans/create-pull-request@v4
         with:
-          base: 'master'
+          base: 'main'
           branch: 'releases/${{ inputs.name }}.mergeback'
           add-paths: |
             **/CHANGELOG.md

.github/workflows/private-mirror-sync.yml

@@ -7,7 +7,7 @@ concurrency:
 on:
   push:
     branches:
-      - master
+      - main
 
 jobs:
   sync:

.github/workflows/release-note-changes.yml

@@ -3,7 +3,7 @@ name: Release note changes
 on:
   pull_request:
     branches:
-      - 'master'
+      - 'main'
 
 jobs:
   build:

.github/workflows/update-cpp-sdk-on-release.yml

@@ -7,7 +7,7 @@ on:
   push:
     branches:
       # Change the below line if the main branch is renamed.
-      - 'master'
+      - 'main'
     paths:
       # Only run this if a gradle.properties file is touched.
       - '**/gradle.properties'