Include introduction only in new GitHub reviews (#27)

We're expanding the introduction text in the PR body to include more
information, and it isn't helpful to include that information in
follow-up reviews. If there are any reviews on a PR from
'github-actions[bot]' already, assume it was us.

rosdistro_reviewer/submitter/github.py

@@ -16,10 +16,12 @@
 GITHUB_TOKEN_ENVIRONMENT_VARIABLE = EnvironmentVariable(
     'GITHUB_TOKEN', 'Authentication token secret for GitHub')
 
-BODY_HEADER = """Hi there, thanks for contributing to ROS!
+INTRODUCTION = """Hi there, thanks for contributing to ROS!
 
 This is an automated review generated by the [rosdistro-reviewer tool](https://github.com/ros-infrastructure/rosdistro-reviewer). If you'd like the tool to run again, just [re-request review from GitHub Actions](https://github.com/ros-infrastructure/rosdistro-reviewer?tab=readme-ov-file#running-rosdistro-reviewer-in-github-actions).
 
+---
+
 """  # noqa: E501
 
 
@@ -91,7 +93,14 @@ def _annotation_to_comment(
         message = review.summarize()
         recommendation = review.recommendation
 
+        # Check if we've already posted a review for this PR
+        already_reviewed = any(
+            review.user.login == 'github-actions[bot]'
+            for review in pr.get_reviews())
+        if not already_reviewed:
+            message = INTRODUCTION + message
+
         pr.create_review(
-            body=BODY_HEADER + message,
+            body=message,
             event=RECOMMENDATION_EVENTS[recommendation],
             comments=comments)

test/spell_check.words

@@ -26,6 +26,7 @@ lenny
 libdelta
 linter
 linting
+login
 mantic
 metafunc
 mktemp