@@ -16,6 +16,7 @@ jobs:
     runs-on: ubuntu-slim
     permissions:
       pull-requests: write
+      statuses: write
     steps:
       - name: Download artefacts
         uses: actions/download-artifact@9000827ccba6bdab643e8b6fd33ac0654aef8333  # v8.0.2
@@ -41,30 +42,49 @@ jobs:
           set -x
           > requisites-before.list
           > requisites-after.list
-          TABLE=$(
+          {
             echo '| Platform | Number of requisites | Proportion of new derivations |'
             echo '| :-: | -: | -: |'
             TOTAL_BEFORE=0
             TOTAL_AFTER=0
             TOTAL_CHANGED=0
             QUOTE='`'
             for PLATFORM in x86_64-linux aarch64-linux x86_64-darwin aarch64-darwin; do
+              if [ ! -f "requisites-${PLATFORM}-before.list" ] || [ ! -f "requisites-${PLATFORM}-after.list" ]; then
+                echo "| ${QUOTE}${PLATFORM}${QUOTE} | _missing data_ | _missing data_ |"
+                continue
+              fi
               BEFORE=$(wc -l < "requisites-${PLATFORM}-before.list")
               TOTAL_BEFORE=$(($TOTAL_BEFORE + $BEFORE))
               AFTER=$(wc -l < "requisites-${PLATFORM}-after.list")
               TOTAL_AFTER=$(($TOTAL_AFTER + $AFTER))
               DIFF="_no changes_"
               [ "$BEFORE" = "$AFTER" ] || DIFF="**$([ "$AFTER" -lt "$BEFORE" ] || echo '+')$(($AFTER - $BEFORE))**"
-              CHANGED=$(git diff --no-index "requisites-${PLATFORM}-before.list" "requisites-${PLATFORM}-after.list" | grep -c '^+[^+]')
+              CHANGED=$(git diff --no-index "requisites-${PLATFORM}-before.list" "requisites-${PLATFORM}-after.list" | grep -c '^+[^+]' || true)
               TOTAL_CHANGED=$(($TOTAL_CHANGED + $CHANGED))
               PERCENT=100
               [ "$CHANGED" = "$AFTER" ] || {
                 PERMILLE=$((1000 * $CHANGED / $AFTER))
                 PERCENT="$((PERMILLE / 10)).$((PERMILLE % 10))"
               }
               echo "| ${QUOTE}${PLATFORM}${QUOTE} | $BEFORE -> $AFTER => $DIFF | $CHANGED / $AFTER = $PERCENT% |"
-              awk '{ print $0 " ('"$PLATFORM"')" }' "requisites-${PLATFORM}-before.list" >> requisites-before.list
-              awk '{ print $0 " ('"$PLATFORM"')" }' "requisites-${PLATFORM}-after.list" >> requisites-after.list
+              for STATE in before after; do
+                # Split store paths into package name and version; non-default outputs are appended to the name (e.g. `brotli.lib`).
+                awk -v OFS='\t' -v PLATFORM="$PLATFORM" '{
+                  name = substr($0, 45)
+                  pname = name
+                  version = "_unversioned_"
+                  if (match(name, /-[^A-Za-z]/)) {
+                    pname = substr(name, 1, RSTART - 1)
+                    version = substr(name, RSTART + 1)
+                    if (match(version, /-[a-z]+$/)) {
+                      pname = pname "." substr(version, RSTART + 1)
+                      version = substr(version, 1, RSTART - 1)
+                    }
+                  }
+                  print pname, version, PLATFORM, $0
+                }' "requisites-${PLATFORM}-${STATE}.list" >> "requisites-${STATE}.list"
+              done
             done
 
             DIFF="_no changes_"
@@ -75,24 +95,79 @@ jobs:
               PERCENT="$((PERMILLE / 10)).$((PERMILLE % 10))"
             }
             echo "| **Total** | $TOTAL_BEFORE -> $TOTAL_AFTER => $DIFF | $TOTAL_CHANGED / $TOTAL_AFTER = $PERCENT% |"
-          )
-          sort -k1.45 requisites-before.list > requisites-before.sort
-          sort -k1.45 requisites-after.list > requisites-after.sort
+          } > comment.md
+          sort requisites-before.list > requisites-before.sort
+          sort requisites-after.list > requisites-after.sort
           if git diff -U0 --no-color --no-index requisites-before.sort requisites-after.sort > requisites.diff; then
             echo 'No changes detected.'
           else
-          {
-            echo "$TABLE"
-            echo
-            echo '<details><summary>Changelog</summary>'
-            echo
-            echo '```diff'
-            tail -n +5 requisites.diff
-            echo '```'
-            echo
-            echo '</details>'
-          } | gh pr comment -R "$GITHUB_REPOSITORY" "$PR_NUMBER" -F -
+            awk -F '\t' '
+              function insert(list, v,    n, a, i, out, done) {
+                n = split(list, a, " ")
+                for (i = 1; i <= n; i++) if (a[i] == v) return list
+                out = ""; done = 0
+                for (i = 1; i <= n; i++) {
+                  if (!done && v < a[i]) { out = out " " v; done = 1 }
+                  out = out " " a[i]
+                }
+                if (!done) out = out " " v
+                return substr(out, 2)
+              }
+              function join(list, pre, post,    s) {
+                s = pre list post
+                gsub(/ /, post ", " pre, s)
+                return s
+              }
+              /^[-+]/ && NF == 4 {
+                key = substr($1, 2) SUBSEP $3
+                if (substr($1, 1, 1) == "-") removed[key] = insert(removed[key], $2)
+                else added[key] = insert(added[key], $2)
+              }
+              END {
+                for (key in removed) if (!(key in added)) added[key] = ""
+                for (key in added) {
+                  split(key, k, SUBSEP)
+                  r = (key in removed) ? removed[key] : ""
+                  a = added[key]
+                  if (r == a) change = "_no version change_: " join(a)
+                  else if (r == "") change = "_added_: " join(a, "**", "**")
+                  else if (a == "") change = "_removed_: " join(r)
+                  else change = join(r) " -> " join(a, "**", "**")
+                  group[k[1] SUBSEP change] = insert(group[k[1] SUBSEP change], k[2])
+                }
+                for (g in group) {
+                  split(g, k, SUBSEP)
+                  rank = k[2] ~ /^_added_/ ? 0 : k[2] ~ /^_removed_/ ? 2 : k[2] ~ /^_no version change_/ ? 3 : 1
+                  print rank "\t| `" k[1] "` | " k[2] " | " join(group[g]) " |"
+                }
+              }
+            ' requisites.diff > versions.tsv
+            {
+              echo
+              echo '<details><summary>Version changes</summary>'
+              echo
+              echo '| Package | Version | Platforms |'
+              echo '| :- | :- | :- |'
+              LC_ALL=C sort -t '`' -k1,1 -k2,2 -k3 versions.tsv | cut -f2-
+              echo
+              echo '</details>'
+            } >> comment.md
+            gh pr comment -R "$GITHUB_REPOSITORY" "$PR_NUMBER" -F comment.md
           fi
         env:
           GH_TOKEN: ${{ github.token }}
           PR_NUMBER: ${{ steps.pr-data.outputs.NUMBER }}
+
+      - name: Report status on the PR
+        if: ${{ always() }}
+        run: |
+          gh api --method POST "repos/${GITHUB_REPOSITORY}/statuses/${HEAD_SHA}" \
+            -f state="$STATE" \
+            -f context="$GITHUB_WORKFLOW" \
+            -f description="$DESCRIPTION" \
+            -f target_url="${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID}"
+        env:
+          GH_TOKEN: ${{ github.token }}
+          HEAD_SHA: ${{ github.event.workflow_run.head_sha }}
+          STATE: ${{ job.status == 'success' && 'success' || 'failure' }}
+          DESCRIPTION: ${{ job.status == 'success' && 'Nix requisites changes aggregated' || 'Failed to aggregate Nix requisites changes' }}