Post a readable diff of changed custom G-code on profile PRs (#16605)

A profile stores each custom G-code setting as one JSON string, so GitHub
shows a G-code edit as one long changed line and reviewers cannot see
what changed.

Add a gcode-diff command to orca_profile_tool.py. For each changed
profile file it decodes, on both sides, every *_gcode and multiline
string option PrintConfig.cpp defines, the options Tab.cpp edits as
code, and any string value that spans several lines. It prints one
collapsed unified diff per setting as markdown. Files with the same diff
for a setting share one section. Trailing spaces are removed, file names
cannot mention GitHub users, and the output is cut to whole sections to
fit a GitHub comment.

Check profiles runs it between the PR's merge commit and its first
parent and adds the result to its artifact, with a line naming the PR
commit. Post profile check comment posts it under its own marker. It
keeps the comment while the diff is unchanged, edits it in place when
only the commit changed, replaces it when the diff changes, and deletes
it when the PR no longer changes any G-code.

The posting job still runs no PR code. It now posts only when the run
checked the head of the PR the artifact names, which covers the
validation comment too.

.github/workflows/check_profiles.yml

@@ -232,6 +232,31 @@ jobs:
           mkdir -p ${{ runner.temp }}/profile-check-results
           echo "${{ github.event.pull_request.number }}" > ${{ runner.temp }}/profile-check-results/pr_number.txt
 
+      # Builds a readable diff of the custom G-code the PR changes, which GitHub shows as
+      # one long line per setting, for check_profiles_comment.yml to post.
+      - name: Diff custom G-code
+        if: ${{ always() && github.event_name == 'pull_request' }}
+        continue-on-error: true
+        env:
+          PR_HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+        run: |
+          git fetch --no-tags --depth=2 origin "$(git rev-parse HEAD)"
+          results=${{ runner.temp }}/profile-check-results
+          diff=${{ runner.temp }}/gcode_diff.md
+          # HEAD is the PR's merge commit, so HEAD^1 is the base it merges onto.
+          python3 ./scripts/orca_profile_tool.py gcode-diff --base HEAD^1 --head HEAD > "$diff"
+          if [ -s "$diff" ]; then
+            {
+              echo "<!-- profile-gcode-diff-comment -->"
+              cat "$diff"
+              echo ""
+              # The comment workflow finds this line as the only one starting with <sub>.
+              echo "<sub>For commit ${PR_HEAD_SHA} of this PR.</sub>"
+            } > "$results/gcode_diff.md"
+          fi
+          # Tells the comment workflow that a missing gcode_diff.md means no G-code changed.
+          touch "$results/gcode_diff_done.txt"
+
       - name: Prepare comment artifact
         if: ${{ always() && github.event_name == 'pull_request' && (steps.profile_tool.outcome == 'failure' || steps.legacy_compat.outcome == 'failure' || steps.validate_system.outcome == 'failure' || steps.validate_slice.outcome == 'failure' || steps.validate_filament_subtypes.outcome == 'failure' || steps.validate_custom.outcome == 'failure') }}
         run: |

.github/workflows/check_profiles_comment.yml

@@ -38,6 +38,7 @@ jobs:
         env:
           GH_TOKEN: ${{ github.token }}
           GH_REPO: ${{ github.repository }}
+          HEAD_SHA: ${{ github.event.workflow_run.head_sha }}
         run: |
           if [ ! -f pr_number.txt ]; then
             echo "No pr_number.txt in artifact, skipping."
@@ -49,18 +50,72 @@ jobs:
             echo "Invalid PR number: $PR_NUMBER"
             exit 1
           fi
+          # PR code wrote the artifact, so only a run for the named PR's current head may post.
+          if [ -z "$HEAD_SHA" ]; then
+            echo "The triggering run names no head commit."
+            exit 1
+          fi
+          if ! PR_HEAD=$(gh api "repos/${GH_REPO}/pulls/${PR_NUMBER}" --jq .head.sha); then
+            echo "Cannot look up PR #${PR_NUMBER}."
+            exit 1
+          fi
+          if [ "$HEAD_SHA" != "$PR_HEAD" ]; then
+            echo "${HEAD_SHA} is not the head of PR #${PR_NUMBER}; skipping."
+            exit 0
+          fi
+
+          # Lists every bot comment on the PR, one JSON object per line.
+          COMMENTS=$(gh api --paginate "repos/${GH_REPO}/issues/${PR_NUMBER}/comments" \
+            --jq '.[] | select(.user.login == "github-actions[bot]") | {id, body} | @json')
 
           # Delete prior comments matching the marker (from check_profiles.yml) or the legacy heading.
-          OLD_IDS=$(gh api --paginate "repos/${GH_REPO}/issues/${PR_NUMBER}/comments" \
-            --jq '.[] | select(.user.login == "github-actions[bot]") | select((.body | startswith("<!-- profile-validation-comment -->")) or (.body | startswith("## :x: Profile Validation Errors"))) | .id')
+          OLD_IDS=$(printf '%s\n' "$COMMENTS" | jq -r 'select((.body | startswith("<!-- profile-validation-comment -->")) or (.body | startswith("## :x: Profile Validation Errors"))) | .id')
           for comment_id in $OLD_IDS; do
             echo "Deleting outdated profile-validation comment ${comment_id}"
             gh api -X DELETE "repos/${GH_REPO}/issues/comments/${comment_id}" || true
           done
 
           # Post a new comment only when validation failed (pr_comment.md present).
+          # A failed post fails the job only after the G-code diff is handled.
+          failed=0
           if [ -f pr_comment.md ]; then
-            gh pr comment "$PR_NUMBER" --body-file pr_comment.md
+            gh pr comment "$PR_NUMBER" --body-file pr_comment.md || failed=1
           else
             echo "Validation succeeded; cleaned up prior comments without posting."
           fi
+
+          # Makes the G-code diff comment match gcode_diff.md, or deletes it if there is none.
+          update_gcode_diff_comment() {
+            if [ ! -f gcode_diff_done.txt ]; then
+              echo "The G-code diff step did not finish; leaving any G-code diff comment as it is."
+              return 0
+            fi
+            GCODE_IDS=$(printf '%s\n' "$COMMENTS" | jq -r 'select(.body | startswith("<!-- profile-gcode-diff-comment -->")) | .id')
+            if [ -f gcode_diff.md ] && [ "$(wc -c < gcode_diff.md)" -gt 65536 ]; then
+              echo "gcode_diff.md is over GitHub's comment limit; not posting it."
+              rm gcode_diff.md
+            fi
+            if [ -f gcode_diff.md ] && [ "$(echo "$GCODE_IDS" | wc -w)" -eq 1 ]; then
+              OLD_BODY=$(printf '%s\n' "$COMMENTS" | jq -r --argjson id "$GCODE_IDS" 'select(.id == $id) | .body' | tr -d '\r')
+              NEW_BODY=$(tr -d '\r' < gcode_diff.md)
+              if [ "$OLD_BODY" = "$NEW_BODY" ]; then
+                echo "G-code diff unchanged; keeping comment ${GCODE_IDS}."
+                return 0
+              fi
+              # Edits in place when only the <sub> line differs, since edits notify nobody.
+              if [ "$(grep -v '^<sub>' <<< "$OLD_BODY")" = "$(grep -v '^<sub>' <<< "$NEW_BODY")" ]; then
+                echo "G-code diff unchanged at a new commit; updating comment ${GCODE_IDS}."
+                gh api -X PATCH "repos/${GH_REPO}/issues/comments/${GCODE_IDS}" -F body=@gcode_diff.md > /dev/null
+                return 0
+              fi
+            fi
+            for comment_id in $GCODE_IDS; do
+              echo "Deleting outdated G-code diff comment ${comment_id}"
+              gh api -X DELETE "repos/${GH_REPO}/issues/comments/${comment_id}" || true
+            done
+            if [ -f gcode_diff.md ]; then
+              gh pr comment "$PR_NUMBER" --body-file gcode_diff.md
+            fi
+          }
+          update_gcode_diff_comment
+          exit "$failed"