refactor: try to condense the action in fewer steps

This should make it easier to debug/maintain.

scripts/run.sh

@@ -0,0 +1,61 @@
+#!/bin/sh
+
+. "$GITHUB_ACTION_PATH/scripts/utils.sh"
+
+# Input validation
+if [ "$COMMENT" != "true" ] && [ "$GENERATE_ARTIFACT" != "true" ]; then
+  panic 'Neither comment-on-pr nor generate-artifact is set
+    note: this looks like an error; if it isn'"'"'t disable this action with "step.if"'
+fi
+
+if [ "$DO_COMPARISON" = 'true' ] && [ -z "$JOB_NAME" ]; then
+  panic 'Requested a comparison report but job-name wasn'"'"'t set'
+fi
+
+# Create Size Report (will be uploaded by the upload-artifact action)
+"$GITHUB_ACTION_PATH/scripts/create-report.sh" report.json
+
+# Nothing else to do
+if [ "$COMMENT" != "true" ]; then exit 0; fi
+
+# Find the PR for this commit so we can post a comment on it
+pr_number=
+case "$GITHUB_EVENT_NAME" in
+"pull_request")
+  pr_number=$(jq .number "$GITHUB_EVENT_PATH")
+  log "Triggered by a pull request with index: $pr_number"
+  ;;
+"push")
+  log "Triggered by a push to $GITHUB_REF_NAME autodetecting PR number"
+
+  log "Get PR number for $GITHUB_REF_NAME"
+  prs=$(curl -X 'GET' \
+    "$GITHUB_API_URL/repos/$GITHUB_REPOSITORY/pulls?state=open&sort=recentupdate" \
+    -H "Authorization: token $GITHUB_TOKEN" \
+    -H 'Accept: application/json')
+
+  log "Found these open PRs: $(echo "$prs" | jq '[.[] | .number]')"
+
+  pr_number=$(echo "$prs" |
+    jq --arg ref "$GITHUB_REF_NAME" '.[] | select(.head.ref == $ref) | .number')
+
+  # Protect against running before a PR is made or if it is triggered on the main branch
+  if [ -z "$pr_number" ]; then
+    warn "No PR created for this commit"
+    exit 0
+  fi
+
+  log "The PR we found for $GITHUB_REF_NAME is $pr_number"
+  ;;
+*)
+  panic "Unexpected event $GITHUB_EVENT_NAME for commenting on a PR, expected push or pull_request"
+  ;;
+esac
+
+log "Expected PR URL: $GITHUB_SERVER_URL/$GITHUB_REPOSITORY/pulls/$pr_number"
+
+# This seems to create the file???
+log "GITHUB_OUTPUT=$GITHUB_OUTPUT"
+log "$(ls -l "$GITHUB_OUTPUT")"
+
+echo "pr-number=$pr_number" >>"$GITHUB_OUTPUT"