add cacompatibility for gh latest main branch (#66)

diff --git a/README.md b/README.md
index 64df458..e520e3a 100644
--- a/README.md
+++ b/README.md
@@ -35,6 +35,7 @@
       uses: ad-m/github-push-action@master
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
+        branch: ${{ github.ref }}
 ```
 
 ### Inputs
@@ -42,7 +43,7 @@
 | name | value | default | description |
 | ---- | ----- | ------- | ----------- |
 | github_token | string | | Token for the repo. Can be passed in using `${{ secrets.GITHUB_TOKEN }}`. |
-| branch | string | 'master' | Destination branch to push changes. |
+| branch | string | | Destination branch to push changes. Can be passed in using `${{ github.ref }}`. |
 | force | boolean | false | Determines if force push is used. |
 | tags | boolean | false | Determines if `--tags` is used. |
 | directory | string | '.' | Directory to change to before pushing. |
diff --git a/start.sh b/start.sh
index 824d76d..21c3cbe 100755
--- a/start.sh
+++ b/start.sh
@@ -1,7 +1,6 @@
 #!/bin/sh
 set -e
 
-INPUT_BRANCH=${INPUT_BRANCH:-master}
 INPUT_FORCE=${INPUT_FORCE:-false}
 INPUT_TAGS=${INPUT_TAGS:-false}
 INPUT_DIRECTORY=${INPUT_DIRECTORY:-'.'}