Rename 'master' branch to 'main'

.github/workflows/gradle-java11.yml

@@ -6,11 +6,11 @@ name: Java 11
 on:
   push:
     branches:
-      - master
+      - main
       - 3.*
   pull_request:
     branches:
-      - master
+      - main
       - 3.*
 
 jobs:

.github/workflows/gradle-java15.yml

@@ -6,11 +6,11 @@ name: Java 15
 on:
   push:
     branches:
-      - master
+      - main
       - 3.*
   pull_request:
     branches:
-      - master
+      - main
       - 3.*
 
 jobs:

CONTRIBUTING.adoc

@@ -2,7 +2,7 @@
 
 Spring Cloud is released under the non-restrictive Apache 2.0 license,
 and follows a very standard Github development process, using Github
-tracker for issues and merging pull requests into master. If you want
+tracker for issues and merging pull requests into main. If you want
 to contribute even something trivial please do not hesitate, but
 follow the guidelines below.
 
@@ -39,7 +39,7 @@ added after the original pull request but before a merge.
   than cosmetic changes).
 * Add some Javadocs and, if you change the namespace, some XSD doc elements.
 * A few unit tests would help a lot as well -- someone has to do it.
-* If no-one else is using your branch, please rebase it against the current master (or
+* If no-one else is using your branch, please rebase it against the current main (or
   other target branch in the main project).
 * When writing a commit message please follow https://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html[these conventions],
   if you are fixing an existing issue please add `Fixes gh-XXXX` at the end of the commit

spring-cloud-open-service-broker-docs/build.gradle

@@ -90,7 +90,7 @@ asciidoctor {
 	options doctype: 'book', eruby: 'erubis'
 	attributes 'revnumber': project.version,
 			'spring-version': project.version,
-			'branch-or-tag': project.version.endsWith('SNAPSHOT') ? 'master' : "v${project.version}",
+			'branch-or-tag': project.version.endsWith('SNAPSHOT') ? 'main' : "v${project.version}",
 			'icons': 'font',
 			'idprefix': '',
 			'idseparator': '-',