Support retrieving changed files between the last remote commit and the current HEAD for push events (#236)

* Update entrypoint.sh

* Update entrypoint.sh

* Update entrypoint.sh

* Update entrypoint.sh

* Update entrypoint.sh

* Update entrypoint.sh

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Update entrypoint.sh

* Update entrypoint.sh

* Update entrypoint.sh

* Update entrypoint.sh

* Create new.yml

* Empty commit

* Empty commit 2

* Empty commit 3

* Updated the use the last remote commit

* Update entrypoint.sh

* Update README.md

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

action.yml

@@ -26,6 +26,10 @@ inputs:
   base_sha:
     description: 'Specify a base commit SHA on used for comparing changes'
     required: false
+  since_last_remote_commit:
+    description: 'Use the last commit on the remote branch as the base_sha for push event.'
+    required: false
+    default: 'false'
   path:
     description: 'Specify a relative path under $GITHUB_WORKSPACE to locate the repository'
     required: false
@@ -90,6 +94,14 @@ runs:
       env:
         INPUT_FILES: ${{ inputs.files }}
         INPUT_FILES_FROM_SOURCE_FILE: ${{ inputs.files_from_source_file }}
+    - run: |
+        if [[ -n "${{ inputs.base_sha }}" ]]; then
+          echo "::set-output name=base_sha::${{ inputs.base_sha }}"
+        elif [[ "${{ github.event_name }}" == "push" && -z "${{ inputs.base_sha }}" && "${{ inputs.since_last_remote_commit }}" == "true" ]]; then
+          echo "::set-output name=base_sha::${{ github.event.before }}"
+        fi
+      id: base-sha
+      shell: bash
     - run: |
         bash $GITHUB_ACTION_PATH/entrypoint.sh
       id: changed-files
@@ -101,7 +113,7 @@ runs:
         # INPUT_<VARIABLE_NAME> is not available in Composite run steps
         # https://github.community/t/input-variable-name-is-not-available-in-composite-run-steps/127611
         INPUT_SHA: ${{ inputs.sha }}
-        INPUT_BASE_SHA: ${{ inputs.base_sha }}
+        INPUT_BASE_SHA: ${{ steps.base-sha.outputs.base_sha }}
         INPUT_TOKEN: ${{ inputs.token }}
         INPUT_FILES: ${{ steps.source-input-files.outputs.files }}
         INPUT_SEPARATOR: ${{ inputs.separator }}