Added action code

Dockerfile

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+FROM python:3
+COPY entrypoint.sh /entrypoint.sh
+ENTRYPOINT ["/entrypoint.sh"]

action.yml

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+name: 'Autopep8'
+description: 'Automatically runs the autopep8 command against any pull request created.'
+
+author: Conrad Großer <grosserconrad@gmail.com>
+
+inputs:
+  commit_message:
+    description: Commit message
+    required: false
+    default: 'Adjusted files for PEP-8 compliance'
+  commit_options:
+    description: Commit options
+    required: false
+  file_pattern:
+    description: File pattern used for "git add"
+    required: false
+    default: '*'
+  dependencies:
+    description: Path for the repositories 'requirements.txt'. If you have none, you may skip this.
+    required: false
+    default: 'false'
+  branch:
+    description: Branch which the changes are merged to
+    required: true
+
+runs:
+  using: 'docker'
+  image: 'Dockerfile'
+  args:
+    - ${{ inputs.commit_message }}
+    - ${{ inputs.commit_options }}
+    - ${{ inputs.file_pattern }}
+    - ${{ inputs.dependencies }}
+    - ${{ inputs.branch }}
+
+branding:
+  icon: 'fast-forward'
+  color: 'green'

entrypoint.sh

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+#!/bin/sh -l
+
+set -eu
+
+# Function for setting up git env in the docker container (copied from https://github.com/stefanzweifel/git-auto-commit-action/blob/master/entrypoint.sh)
+git_setup ( ) {
+  cat <<- EOF > $HOME/.netrc
+        machine github.com
+        login $GITHUB_ACTOR
+        password $GITHUB_TOKEN
+        machine api.github.com
+        login $GITHUB_ACTOR
+        password $GITHUB_TOKEN
+EOF
+    chmod 600 $HOME/.netrc
+
+    git config --global user.email "actions@github.com"
+    git config --global user.name "GitHub Actions"
+}
+
+echo "Installing dependencies..."
+pip install --upgrade pip
+# Install dependencies
+pip install autopep8
+
+# Install custom project dependencies if applicable
+if ! $INPUT_DEPENDENCIES == "false"
+then
+  pip install -r $INPUT_DEPENDENCIES
+fi
+
+# Apply PEP 8
+echo "Running autopep8..."
+autopep8 --in-place -r .
+
+if ! git diff --quiet
+then
+  echo "Commiting and pushing changes."
+  # Calling method to configure the git environemnt
+  git_setup
+  # Switch to the actual branch
+  git checkout $INPUT_BRANCH
+
+  git add "${INPUT_FILE_PATTERN}"
+
+  git commit -m "$INPUT_COMMIT_MESSAGE" --author="$GITHUB_ACTOR <$GITHUB_ACTOR@users.noreply.github.com>" ${INPUT_COMMIT_OPTIONS:+"$INPUT_COMMIT_OPTIONS"}
+  git push --set-upstream origin "HEAD:$INPUT_BRANCH"
+else
+  echo "Nothing to commit. Exiting."
+fi