Replace references to 'master' with 'main'

Signed-off-by: Josh Dolitsky <josh@dolit.ski>

.github/workflows/release.yml

@@ -3,7 +3,7 @@ name: release
 on:
   push:
     branches:
-      - master
+      - main
     tags:
       - v*
 

.pullapprove.yml

@@ -20,7 +20,7 @@ group_defaults:
     ignored: true
   conditions:
     branches:
-      - master
+      - main
 
 groups:
   distribution-spec:

MAINTAINERS_GUIDE.md

@@ -57,7 +57,7 @@ All decisions affecting this project, big and small, follow the same procedure:
 
 ### I'm a maintainer, should I make pull requests too?
 
-Yes. Nobody should ever push to master directly. All changes should be
+Yes. Nobody should ever push to main directly. All changes should be
 made through a pull request.
 
 ## Who decides what?

conformance/README.md

@@ -203,7 +203,7 @@ This will create a local `results/` directory containing all of the test report
 A GitHub Action is provided by this repo which you can use
 as part of a GitHub-based CI pipeline.
 
-The following example will build the binary off of the master branch,
+The following example will build the binary off of the main branch,
 run the tests, and upload `junit.xml` and `report.html` as build artifacts:
 
 ```yaml
@@ -215,7 +215,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Run OCI Distribution Spec conformance tests
-        uses: opencontainers/distribution-spec@master
+        uses: opencontainers/distribution-spec@main
         env:
           OCI_ROOT_URL: https://myreg.io
           OCI_NAMESPACE: mytestorg/mytestrepo