Replace --create-if-missing to --update-only

`--update-only` is disabled by default, whereas `--create-if-missing` should've been enabled by default but was not.

.github/actions/post-comment/action.yml

@@ -9,12 +9,10 @@ inputs:
   body:
     description: "Full comment markdown."
     required: true
-  create-if-missing:
-    description: >
-      Create a comment if no matching marker exists.
-      Set to 'false' to update existing comments only.
+  update-only:
+    description: Do nothing if no comment with the specified marker exists.
     required: false
-    default: "true"
+    default: "false"
   issue-id:
     description: >
       The issue or pull request number to post/update the comment on.
@@ -31,13 +29,13 @@ runs:
       env:
         BODY: ${{ inputs.body }}
         MARKER: ${{ inputs.marker }}
-        CREATE_IF_MISSING: ${{ (inputs.create-if-missing == 'true' && '--create-if-missing') || '' }}
+        UPDATE_ONLY: ${{ (inputs.update-only == 'true' && '--update-only') || '' }}
         GH_TOKEN: ${{ inputs.token }}
         ISSUE_ID: ${{ inputs.issue-id || github.event.pull_request.number }}
       run: |
         npx tsx ./pr-checks/post-comment.ts \
           --body "$BODY" \
           --marker "$MARKER" \
-          $CREATE_IF_MISSING \
+          $UPDATE_ONLY \
           --issue-id "$ISSUE_ID" \
           --repository "$GITHUB_REPOSITORY"

.github/workflows/pr-checks.yml

@@ -307,7 +307,7 @@ jobs:
 
       - name: Mark the CHANGELOG.md concern as resolved
         if: >-
-          needs.other-checks.outputs.changelog-modified != 'true' &&
+          needs.other-checks.outputs.changelog-modified == 'false' &&
           !startsWith(github.event.pull_request.head.ref, 'update-v') &&
           !startsWith(github.event.pull_request.head.ref, 'backport-v') &&
           !startsWith(github.event.pull_request.head.ref, 'mergeback/') &&
@@ -315,7 +315,7 @@ jobs:
         uses: ./.github/actions/post-comment
         with:
           marker: "post-comment:CHANGELOG.md"
-          create-if-missing: "false"
+          update-only: true
           body: |
             ⚠️ `CHANGELOG.md` has been modified in this PR. Please do not modify `CHANGELOG.md` directly.
             Instead, create a change-note file in `unreleased-change-notes/`. The `CHANGELOG.md`

pr-checks/post-comment.test.ts

@@ -49,15 +49,15 @@ describe("parseOptions", async () => {
     assert.deepEqual(options, {
       body: "hello",
       marker: "marker",
-      createIfMissing: false,
+      updateOnly: false,
       issueId: 42,
       repository: { owner: "github", repo: "codeql-action" },
     });
   });
 
-  await it("enables creation when --create-if-missing is supplied", () => {
-    const options = parseOptions([...validFlags, "--create-if-missing"]);
-    assert.equal(options.createIfMissing, true);
+  await it("enables update-only mode when --update-only is supplied", () => {
+    const options = parseOptions([...validFlags, "--update-only"]);
+    assert.equal(options.updateOnly, true);
   });
 
   await it("rejects a missing --body", () => {
@@ -212,7 +212,7 @@ describe("findExistingComment", async () => {
 const baseOptions: Options = {
   body: "hello",
   marker: "marker",
-  createIfMissing: true,
+  updateOnly: false,
   issueId: 42,
   repository: { owner: "owner", repo: "repo" },
 };
@@ -227,20 +227,20 @@ function assertCommentContent(
 }
 
 describe("setComment", async () => {
-  await it("does not create a resolved comment when no comments exist", async () => {
+  await it("does not create a comment in update-only mode when none exists", async () => {
     const { client, comments } = fakeClient([]);
 
-    await setComment(client, { ...baseOptions, createIfMissing: false });
+    await setComment(client, { ...baseOptions, updateOnly: true });
 
     // Resolution does not introduce a warning that was never posted.
     assert.deepEqual(comments, []);
   });
 
-  await it("leaves unrelated comments unchanged when creation is disabled", async () => {
+  await it("leaves unrelated comments unchanged in update-only mode", async () => {
     const originalComments = [{ id: 7, body: "unrelated" }];
     const { client, comments } = fakeClient(originalComments);
 
-    await setComment(client, { ...baseOptions, createIfMissing: false });
+    await setComment(client, { ...baseOptions, updateOnly: true });
 
     // Unrelated comments neither trigger resolution nor get overwritten.
     assert.deepEqual(comments, originalComments);
@@ -334,7 +334,7 @@ describe("setComment", async () => {
     const body =
       "`CHANGELOG.md` is not modified in this PR. No changelog action is needed.";
 
-    await setComment(client, { ...baseOptions, body, createIfMissing: false });
+    await setComment(client, { ...baseOptions, body, updateOnly: true });
 
     // The resolved state replaces the warning on the same marked comment.
     assert.equal(comments.length, 1);

pr-checks/post-comment.ts

@@ -5,12 +5,11 @@ Creates or updates a pull request comment identified by a marker. The marker
 is supplied via `--marker` (or the `.github/actions/post-comment` action's `marker` input)
 and must be non-empty. Supply a plain-text identifier; the CLI wraps it in a
 hidden HTML comment, prepends it to `--body`, and uses it to find the comment on later runs.
-Supply `--create-if-missing` to allow creation; omit it to update existing comments only.
+Supply `--update-only` to suppress creation; omit it to update or create comments.
 
 Example:
 ```sh
 GH_TOKEN=<token> npx tsx ./pr-checks/post-comment.ts \
-  --create-if-missing \
   --body "The changelog needs updating." \
   --marker "my-bot" \
   --issue-id 123 \
@@ -31,8 +30,8 @@ export interface Options {
   body: string;
   /** Plain-text identifier wrapped in a hidden HTML comment. */
   marker: string;
-  /** Whether to create a comment when no matching marker exists. */
-  createIfMissing: boolean;
+  /** Whether to only update a comment if a matching marker exists. */
+  updateOnly: boolean;
   /** The issue/pull request number to post/update the comment on. */
   issueId: number;
   /** The repository to operate on. */
@@ -50,7 +49,7 @@ export function parseOptions(argv?: string[]): Options {
     options: {
       body: { type: "string" },
       marker: { type: "string" },
-      "create-if-missing": { type: "boolean", default: false },
+      "update-only": { type: "boolean", default: false },
       "issue-id": { type: "string" },
       repository: { type: "string" },
     },
@@ -80,7 +79,7 @@ export function parseOptions(argv?: string[]): Options {
   return {
     body: values.body,
     marker: values.marker,
-    createIfMissing: values["create-if-missing"],
+    updateOnly: values["update-only"],
     issueId: Number(values["issue-id"]),
     repository: parseRepositoryNwo(values.repository),
   };
@@ -131,9 +130,9 @@ export async function setComment(
     marker,
   );
   if (existingCommentId === undefined) {
-    if (!options.createIfMissing) {
+    if (options.updateOnly) {
       console.info(
-        "No existing comment found; skipping creation because --create-if-missing wasn't specified.",
+        "No existing comment found; skipping creation because --update-only was specified.",
       );
       return;
     }