Add bot comment with directions to update .mailmap (#1982)

* Add bot comment with directions to update .mailmap

* Edit comment content

* Rename workflow file

.github/workflows/mailmap.yml

@@ -0,0 +1,46 @@
+# For more information on how to use this template please refer to:
+# http://tardis-sn.github.io/tardis/development/continuous_integration.html
+
+name: mailmap
+
+on:
+  pull_request_target:
+    branches:
+      - master
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+
+      - name: Check PR authors
+        run: cat .mailmap | grep "$(git log $PR_BASE_SHA..HEAD --pretty='%aN <%aE>')"
+        env:
+          PR_BASE_SHA: ${{ github.event.pull_request.base.sha }}
+
+      - name: Error message
+        run: |
+          echo "Committer name or email couldn't be found in .mailmap"
+          echo; git log $PR_BASE_SHA..HEAD --pretty='%aN <%aE>'
+        if: failure()
+
+      - name: Create comment
+        uses: peter-evans/create-or-update-comment@v2
+        with:
+          token: ${{ secrets.BOT_TOKEN }}
+          issue-number: ${{ github.event.pull_request.number }}
+          body: |
+            *\*beep\* \*bop\**
+
+            Hi, human.
+
+            I'm the @tardis-bot and couldn't find your records in my database. I think we don't know each other, or you changed your credentials recently.
+
+            Please add your **name** and **email** to `.mailmap` in your current branch and push the changes to this pull request.
+
+            In case you need to map an existing alias, follow [this example](https://docs.enterprise.codescene.io/versions/2.0.0/getting-started/ensure-you-use-a-mailmap.html).
+        if: failure()