Added basic functionality

action.yml

@@ -0,0 +1,19 @@
+name: Changelog Action
+description: Automatically creates a changelog for Pull Requests
+
+author: Conrad Großer <grosserconrad@gmail.com>
+
+runs:
+  using: "composite"
+  steps:
+    - name: Prettify code!
+      shell: bash
+      run: >-
+        ${{ github.action_path }}/entrypoint.sh
+      env:
+        INPUT_HEAD_REF: ${{ github.head_ref }}
+        INPUT_REF: ${{ github.ref }}
+
+branding:
+  icon: "activity"
+  color: "green"

entrypoint.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+# e is for exiting the script automatically if a command fails, u is for exiting if a variable is not set
+# x would be for showing the commands before they are executed
+set -eux
+
+git log --oneline --decorate $INPUT_HEAD_REF..$INPUT_REF --format=%B -n 1