fix: Extended github script to split large diffs into multiple commen…

…ts, using summary comments instead of full blocks, excluding empty files from diff comments

render-and-diff-helm/action.yml

@@ -5,6 +5,7 @@
 name: Matrix render and diff helm charts
 description: Renders BASE and REF helm charts then posts the diff of the rendered charts as a comment on the pull request 
 
+
 on:
   workflow_call:
     inputs:
@@ -35,7 +36,7 @@ jobs:
           git fetch origin ${{ github.base_ref }}:${{ github.base_ref }}
           echo matrix_changed_charts=$(git diff --name-only ${{ github.base_ref }}...HEAD -- '**/k8s/**/*.yaml' '**/k8s/**/*.yml' '**/k8s/**/*.tpl' '**/k8s/**/*.tmpl' | cut -d'/' -f1,2,3 | uniq | jq -R 'split("\n")' | jq -s 'flatten(1)') >> $GITHUB_OUTPUT
           echo changed_charts=$(git diff --name-only ${{ github.base_ref }}...HEAD -- '**/k8s/**/*.yaml' '**/k8s/**/*.yml' '**/k8s/**/*.tpl' '**/k8s/**/*.tmpl' | cut -d'/' -f1,2,3 | uniq) >> $GITHUB_OUTPUT
-    
+
   render_head_ref_charts:
     runs-on: ubuntu-latest
     needs: get_changed_helm_charts
@@ -54,13 +55,16 @@ jobs:
         run: |
           mkdir -p shared/head-charts
           git fetch origin ${{ github.head_ref }}
-          git checkout  ${{ github.head_ref }}
-          values_files="${{ matrix.chart }}"/values-*
-          for values_file in $(basename -a $values_files); do
-            helm template "${{ matrix.chart }}" -f "${{ matrix.chart }}/values.yaml" -f "${{ matrix.chart }}/${values_file}" --output-dir "shared/head-charts/${{ matrix.chart }}/${values_file}"
-          done
+          git checkout  ${{ github.head_ref }} --
+          if [ -d "${{ matrix.chart }}" ]; then
+            helm dependency build "${{ matrix.chart }}"
+            values_files="${{ matrix.chart }}"/values-*
+            for values_file in $(basename -a $values_files); do
+              helm template "${{ matrix.chart }}" -f "${{ matrix.chart }}/values.yaml" -f "${{ matrix.chart }}/${values_file}" --output-dir "shared/head-charts/${{ matrix.chart }}/${values_file}"
+            done
+          fi
           echo sanitized_name=$(echo "${{ matrix.chart }}" | sed 's/\//-/g') >> $GITHUB_OUTPUT
-
+          echo "${{ matrix.chart }} does not exist in ${{ github.base_ref }} ref"
       - name: upload artifact
         uses: actions/upload-artifact@v4
         with:
@@ -85,13 +89,16 @@ jobs:
         run: |
           mkdir -p shared/base-charts
           git fetch origin ${{ github.base_ref }}
-          git checkout  ${{ github.base_ref }}
-          values_files="${{ matrix.chart }}"/values-*
-          for values_file in $(basename -a $values_files); do
-            helm template "${{ matrix.chart }}" -f "${{ matrix.chart }}/values.yaml" -f "${{ matrix.chart }}/${values_file}" --output-dir "shared/base-charts/${{ matrix.chart }}/${values_file}"
-          done
+          git checkout  ${{ github.base_ref }} --
+          if [ -d "${{ matrix.chart }}" ]; then
+            helm dependency build "${{ matrix.chart }}"
+            values_files="${{ matrix.chart }}"/values-*
+            for values_file in $(basename -a $values_files); do
+              helm template "${{ matrix.chart }}" -f "${{ matrix.chart }}/values.yaml" -f "${{ matrix.chart }}/${values_file}" --output-dir "shared/base-charts/${{ matrix.chart }}/${values_file}"
+            done
+          fi
           echo sanitized_name=$(echo "${{ matrix.chart }}" | sed 's/\//-/g') >> $GITHUB_OUTPUT
-
+          echo "${{ matrix.chart }} does not exist in ${{ github.base_ref }} ref"
       - name: upload artifact
         uses: actions/upload-artifact@v4
         with:
@@ -100,7 +107,7 @@ jobs:
 
   diff_helm_charts:
     runs-on: ubuntu-latest
-    needs: 
+    needs:
       - get_changed_helm_charts
       - render_base_ref_charts
       - render_head_ref_charts
@@ -121,21 +128,54 @@ jobs:
           for chart in ${{ needs.get_changed_helm_charts.outputs.charts }}; do
             chart_diff_output=$(diff -r "shared/base-charts/${chart}" "shared/head-charts/${chart}" || true)
             if [ -n "$chart_diff_output" ]; then
-              echo -e "Changes found in chart: ${chart}\n$(diff -ruN shared/base-charts/${chart} shared/head-charts/${chart})\n" >> diff.log
+              echo -e "Changes found in chart: ${chart}\n$(diff -ru shared/base-charts/${chart} shared/head-charts/${chart})\n" >> diff.log
             fi
           done
-
       - name: post diff as comment on pull request
         if: needs.get_changed_helm_charts.outputs.charts != ''
         uses: actions/github-script@v7
         with:
           script: |
             const fs = require('fs');
+            const comment_char_limit = 65536; // GitHub comment character limit
             const diff = fs.readFileSync('diff.log', 'utf8');
-            
-            github.rest.issues.createComment({
-              issue_number: context.issue.number,
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              body: '```diff\n' + diff + '\n```'
-            })
+
+            function splitComment(comment, maxSize, sepEnd, sepStart, comStart) {
+              // Adapted from Atlantis SplitComment function
+              // https://github.com/runatlantis/atlantis/blob/main/server/events/vcs/common/common.go#L18
+              if (comment.length <= (comment_char_limit - comStart.length)) {
+                return [comStart + diff]
+              }
+              maxWithSep = comment_char_limit - sepEnd.length - sepStart.length;
+              var comments = [];
+              var numComments = Math.ceil(comment.length / maxWithSep);
+              for (var i = 0; i < numComments; i++) {
+                var upTo = Math.min(comment.length, (i + 1) * maxWithSep);
+                var portion = comment.slice(i * maxWithSep, upTo);
+                if (i < numComments - 1) {
+                  portion += sepEnd;
+                }
+                if (i > 0) {
+                  portion = sepStart + portion
+                } else {
+                  portion = comStart + portion
+                }
+                comments.push(portion);
+              }
+              return comments;
+            }
+
+            var sepEnd = "\n```\n</details>" + "\n<br>\n\n**Warning**: Output length greater than max comment size. Continued in next comment.";
+            var sepStart = "Continued from previous comment.\n<details><summary>Show Output</summary>\n\n" + "```diff\n";
+            var comStart = "Changes found in Helm charts.\n<details><summary>Show Output</summary>\n\n" + "```diff\n";
+
+            comments = splitComment(diff, comment_char_limit, sepEnd, sepStart, comStart);
+
+            for (const comment of comments) {
+              await github.rest.issues.createComment({
+                issue_number: context.issue.number,
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                body: comment
+              })
+            }