Replace 'master' branch references with 'main' (heroku#1029)

For heroku#1028.

.travis.yml

@@ -2,7 +2,7 @@ language: minimal
 dist: bionic
 branches:
   only:
-  - master
+  - main
 
 script:
   - make test STACK="${STACK}" TEST_CMD="${TEST_CMD}"

CHANGELOG.md

@@ -1,7 +1,8 @@
 # Python Buildpack Changelog
 
-# Master
+# Unreleased
 
+- Switch the `heroku-buildpack-python` repository default branch from `master` to `main` (#1029).
 
 # 174 (2020-07-30)
 

README.md

@@ -2,7 +2,7 @@
 
 # Heroku Buildpack: Python
 
-[![Build Status](https://travis-ci.org/heroku/heroku-buildpack-python.svg?branch=master)](https://travis-ci.org/heroku/heroku-buildpack-python)
+[![Build Status](https://travis-ci.com/heroku/heroku-buildpack-python.svg?branch=main)](https://travis-ci.com/heroku/heroku-buildpack-python)
 
 This is the official [Heroku buildpack](https://devcenter.heroku.com/articles/buildpacks) for Python apps.
 
@@ -16,7 +16,7 @@ See it in Action
 $ ls
 my-application		requirements.txt	runtime.txt
 
-$ git push heroku master
+$ git push heroku main
 Counting objects: 4, done.
 Delta compression using up to 8 threads.
 Compressing objects: 100% (2/2), done.

etc/publish.sh

@@ -14,9 +14,9 @@ case "$choice" in
   * ) exit 1;;
 esac
 
-originMaster=$(git rev-parse origin/master)
-echo "Tagging commit $originMaster with $newVersion... "
-git tag "$newVersion" "${originMaster:?}"
+originMain=$(git rev-parse origin/main)
+echo "Tagging commit $originMain with $newVersion... "
+git tag "$newVersion" "${originMain:?}"
 git push origin refs/tags/$newVersion
 
 heroku buildpacks:publish "$BP_NAME" "$newVersion"
@@ -31,7 +31,7 @@ if [ $(git tag | grep -q latest-version) ]; then
     echo "Updating latest-version tag"
     git tag -d latest-version
     git push origin :latest-version
-    git tag latest-version "${originMaster:?}"
+    git tag latest-version "${originMain:?}"
     git push --tags
 fi