Introduce postDiffToGitHubSnippet for unified diff posting and upda…

…te `kubectl.nix` and `terra.nix`

- **Add `postDiffToGitHubSnippet`:**
  - Created a reusable snippet that handles posting unified diffs to GitHub PR comments using the `gh` CLI.
  - Manages existing comments by updating them or creates new ones if necessary.

- **Update `kubectl.nix`:**
  - Replaced inline diff posting logic with the new `postDiffToGitHubSnippet`.

- **Modify `terra.nix`:**
  - Integrated `postDiffToGitHubSnippet` into the `plan` command within the `wrap` function.
  - Exported `TF_VAR_fragment` and `TF_VAR_fragmentRelPath` for use in Terraform configurations.
  - Changed the Terraform working directory to `$PRJ_ROOT/.cache/${fragmentRelPath}/.tf` for better organization.

src/std/fwlib/blockTypes/_postDiffToGitHubSnippet.nix

@@ -0,0 +1,73 @@
+_: path: cmd: script: ''
+
+  if [[ -v CI ]] && [[ -v BRANCH ]] && [[ -v OWNER_AND_REPO ]] && command -v gh > /dev/null ; then
+
+    OWNER_REPO_NAME=$(gh repo view "$OWNER_AND_REPO" --json nameWithOwner --jq '.nameWithOwner')
+
+    if ! gh pr view "$BRANCH" --repo "$OWNER_REPO_NAME" >/dev/null 2>&1; then
+      exit 0
+    fi
+
+    set +e # diff exits 1 if diff existed
+    DIFF_OUTPUT=$(${script})
+    set -e
+
+    if [[ -z "$DIFF_OUTPUT" ]]; then
+      exit 0
+    fi
+
+    CENTRAL_COMMENT_HEADER="<!-- Unified Diff Comment -->"
+    ENTRY_START_MARKER="<!-- Start Diff for ${path}:${cmd} -->"
+    ENTRY_END_MARKER="<!-- End Diff for ${path}:${cmd} -->"
+
+    DIFF_ENTRY=$(cat <<EOF
+
+$ENTRY_START_MARKER
+<details>
+<summary>//${path}:${cmd}</summary>
+
+\`\`\`diff
+$DIFF_OUTPUT
+\`\`\`
+
+</details>
+$ENTRY_END_MARKER
+EOF
+    )
+
+    PR_NUMBER=$(gh pr view "$BRANCH" --repo "$OWNER_REPO_NAME" --json number --jq '.number')
+
+    EXISTING_COMMENT_ID=$(gh api "repos/$OWNER_REPO_NAME/issues/$PR_NUMBER/comments?per_page=100" --jq ".[] | select(.body | contains(\"$CENTRAL_COMMENT_HEADER\")) | .id" | head -n 1)
+
+    if [[ -n "$EXISTING_COMMENT_ID" ]]; then
+      EXISTING_BODY=$(gh api "repos/$OWNER_REPO_NAME/issues/comments/$EXISTING_COMMENT_ID" --jq '.body')
+
+      if echo "$EXISTING_BODY" | grep -q "$ENTRY_START_MARKER"; then
+        UPDATED_BODY=$(echo "$EXISTING_BODY" | sed -e "\#$ENTRY_START_MARKER#,\#$ENTRY_END_MARKER#d")
+      else
+        UPDATED_BODY="$EXISTING_BODY"
+      fi
+
+      UPDATED_BODY="$UPDATED_BODY
+$DIFF_ENTRY"
+
+      echo "Make an edit post ..."
+      gh api --method PATCH "repos/$OWNER_REPO_NAME/issues/comments/$EXISTING_COMMENT_ID" -f body="$UPDATED_BODY" --jq '.html_url'
+
+    else
+      NEW_COMMENT=$(cat <<EOF
+$CENTRAL_COMMENT_HEADER
+## DiffPost
+
+This PR includes the following diffs:
+$DIFF_ENTRY
+EOF
+      )
+      echo "Make a first post ..."
+      gh pr comment "$PR_NUMBER" --repo "$OWNER_REPO_NAME" --body "$NEW_COMMENT"
+    fi
+
+    exit 0
+
+  fi
+''

src/std/fwlib/blockTypes/kubectl.nix

@@ -16,7 +16,7 @@ Available actions:
 */
 let
   inherit (root) mkCommand;
-  inherit (super) addSelectorFunctor askUserToProceedSnippet;
+  inherit (super) addSelectorFunctor askUserToProceedSnippet postDiffToGitHubSnippet;
 in
   name: {
     __functor = addSelectorFunctor;
@@ -137,34 +137,11 @@ in
         } "$manifest_path/";
         }
 
-        # GitHub case
-        if [[ -v CI ]] && [[ -v BRANCH ]] && [[ -v OWNER_AND_REPO ]] && command gh > /dev/null ; then
+        ${postDiffToGitHubSnippet fragmentRelPath "kubectl" "diff"}
 
-          set +e # diff exits 1 if diff existed
-          read -r -d "" DIFFSTREAM <<DIFF
-        ## Standard DiffPost
-
-        This PR would generate the following \`kubectl\` diff:
-
-        <details><summary>Preview</summary>
-
-        \`\`\`diff
-        $(diff)
-        \`\`\`
-
-        </details>
-        DIFF
-          set -e # we're past the invocation of diff
-
-          if ! gh pr --repo "$OWNER_AND_REPO" comment "$BRANCH" --edit-last -b "$DIFFSTREAM"; then
-            echo "Make a first post ..."
-            gh pr --repo "$OWNER_AND_REPO" comment "$BRANCH" -b "$DIFFSTREAM"
-          fi
-        else
-          KUBECTL_EXTERNAL_DIFF="icdiff -N -r"
-          export KUBECTL_EXTERNAL_DIFF
-          diff
-        fi
+        KUBECTL_EXTERNAL_DIFF="icdiff -N -r"
+        export KUBECTL_EXTERNAL_DIFF
+        diff
       '' {})
       (mkCommand currentSystem "apply" "Apply the manifests to K8s" [pkgs.kubectl pkgs.icdiff] ''
         ${build}

src/std/fwlib/blockTypes/terra.nix

@@ -21,11 +21,11 @@ Available actions:
 */
 let
   inherit (root) mkCommand;
-  inherit (super) addSelectorFunctor;
+  inherit (super) addSelectorFunctor postDiffToGitHubSnippet;
 in
   name: repo: {
     inherit name;
-    __functor = self: selectors: self // selectors;
+    __functor = addSelectorFunctor;
     type = "terra";
     actions = {
       currentSystem,
@@ -60,32 +60,47 @@ in
         .config);
 
       setup = ''
+        export TF_VAR_fragment=${pkgs.lib.strings.escapeShellArg fragment}
+        export TF_VAR_fragmentRelPath=${fragmentRelPath}
         export TF_IN_AUTOMATION=1
-        # export TF_INPUT=0
         export TF_DATA_DIR="$PRJ_DATA_HOME/${fragmentRelPath}"
         export TF_PLUGIN_CACHE_DIR="$PRJ_CACHE_HOME/tf-plugin-cache"
         mkdir -p "$TF_DATA_DIR"
         mkdir -p "$TF_PLUGIN_CACHE_DIR"
-        dir="$PRJ_ROOT/${repoFolder}/.tf"
-        mkdir -p "$PRJ_ROOT/${repoFolder}/.tf"
-        cat << MESSAGE > "$PRJ_ROOT/${repoFolder}/.tf/readme.md"
+        dir="$PRJ_ROOT/.cache/${fragmentRelPath}/.tf"
+        mkdir -p "$dir"
+        cat << MESSAGE > "$dir/readme.md"
         This is a tf staging area.
         It is motivated by the terraform CLI requiring to be executed in a staging area.
         MESSAGE
 
         if [[ -e "$dir/config.tf.json" ]]; then rm -f "$dir/config.tf.json"; fi
         jq '.' ${terraformConfiguration} > "$dir/config.tf.json"
       '';
-
-      wrap = cmd: ''
-        ${setup}
-        terraform-backend-git git \
-           --dir "$dir" \
-           --repository ${git.repo} \
-           --ref ${git.ref} \
-           --state ${git.state} \
-           terraform ${cmd} "$@";
-      '';
+      wrap = cmd:
+        setup
+        + (
+          (pkgs.lib.optionalString (cmd == "plan")) (
+            postDiffToGitHubSnippet fragmentRelPath cmd ''
+              terraform-backend-git git \
+                 --dir "$dir" \
+                 --repository ${git.repo} \
+                 --ref ${git.ref} \
+                 --state ${git.state} \
+                 terraform plan \
+                   -lock=false \
+                   -no-color
+            ''
+          )
+        )
+        + ''
+          terraform-backend-git git \
+             --dir "$dir" \
+             --repository ${git.repo} \
+             --ref ${git.ref} \
+             --state ${git.state} \
+             terraform ${cmd} "$@";
+        '';
     in [
       (mkCommand currentSystem "init" "tf init" [pkgs.jq pkgs.terraform pkgs.terraform-backend-git] (wrap "init") {})
       (mkCommand currentSystem "plan" "tf plan" [pkgs.jq pkgs.terraform pkgs.terraform-backend-git] (wrap "plan") {})