Tweaks to case count reports on PRs (#4551)

* Print something when there's no diff

Otherwise it's kind of confusing.

* Also don't post the 'waiting for build job' if there isn't already a comment

* Also don't post an update if it was cancelled

Author: kainino0x

.github/workflows/pr-comment.yml

@@ -41,7 +41,7 @@ jobs:
           body-includes: "<!-- pr-comment -->"
 
       # If 'pr' workflow run was 'requested'...
-      - if: github.event.action == 'requested'
+      - if: github.event.action == 'requested' && steps.find-comment.outputs.comment-id != ''
         name: PR workflow started - Update Comment
         uses: peter-evans/create-or-update-comment@v5
         with:
@@ -52,8 +52,9 @@ jobs:
             <!-- pr-comment -->
             Waiting for [build job](https://github.com/${{github.repository}}/actions/runs/${{github.event.workflow_run.id}}) (at ${{ github.event.workflow_run.head_sha }})...
 
-      # If 'pr' workflow run was 'completed'...
-      - if: github.event.action == 'completed'
+      # If 'pr' workflow run was 'completed' (but not 'cancelled', that usually means a new job is
+      # running, and we don't want to race with it)...
+      - if: github.event.action == 'completed' && github.event.workflow_run.conclusion != 'cancelled'
         name: PR workflow completed - Download pr-comment-body.txt
         uses: actions/download-artifact@v4
         continue-on-error: true
@@ -62,7 +63,7 @@ jobs:
           repository: ${{ github.event.workflow_run.repository.full_name }}
           run-id: ${{ github.event.workflow_run.id }}
           name: pr-comment-body.txt
-      - if: github.event.action == 'completed'
+      - if: github.event.action == 'completed' && github.event.workflow_run.conclusion != 'cancelled'
         name: PR workflow completed - Create pr-comment.txt
         env:
           REPO: ${{github.repository}}
@@ -84,8 +85,8 @@ jobs:
               echo '(No pr-comment-body.txt artifact found from this job.)'
             fi
           ) > pr-comment.txt
-      - if: github.event.action == 'completed'
-        name: PR workflow completed - Update Comment
+      - if: github.event.action == 'completed' && github.event.workflow_run.conclusion != 'cancelled'
+        name: PR workflow completed - Post or Update Comment
         uses: peter-evans/create-or-update-comment@v5
         with:
           issue-number: ${{ steps.pr-context.outputs.number }}

.github/workflows/pr.yml

@@ -53,11 +53,14 @@ jobs:
           diff --unified=0 case-count-report-{before,after}.txt | grep '^[+-][^+-]' | tee case-count-report-diff.txt
           (
             echo '```diff'
-            if [[ "$(wc -l < case-count-report-diff.txt)" -le 20 ]] ; then
+            line_count=$(wc -l < case-count-report-diff.txt)
+            if [[ "${line_count}" -eq 0 ]] ; then
+              echo ' Test case/subcase counts did not change.'
+            elif [[ "${line_count}" -le 20 ]] ; then
               cat case-count-report-diff.txt
             else
               head -n18 case-count-report-diff.txt
-              echo '[snip - full report in action logs]'
+              echo ' [snip - full report in action logs]'
               tail -n2 case-count-report-diff.txt
             fi
             echo '```'