single line comments

src/commenter.ts

@@ -173,17 +173,31 @@ ${tag}`
         core.info(
           `Creating new review comment for ${path}:${start_line}-${end_line}: ${message}`
         )
-        await octokit.pulls.createReviewComment({
-          owner: repo.owner,
-          repo: repo.repo,
-          pull_number,
-          body: message,
-          commit_id,
-          path,
-          line: end_line,
-          start_line,
-          start_side: 'RIGHT'
-        })
+        // if start_line is same as end_line, it's a single line comment
+        // otherwise it's a multi-line comment
+        if (start_line === end_line) {
+          await octokit.pulls.createReviewComment({
+            owner: repo.owner,
+            repo: repo.repo,
+            pull_number,
+            body: message,
+            commit_id,
+            path,
+            line: end_line
+          })
+        } else {
+          await octokit.pulls.createReviewComment({
+            owner: repo.owner,
+            repo: repo.repo,
+            pull_number,
+            body: message,
+            commit_id,
+            path,
+            line: end_line,
+            start_line,
+            start_side: 'RIGHT'
+          })
+        }
       }
     } catch (e) {
       core.warning(
@@ -256,7 +270,7 @@ ${COMMENT_REPLY_TAG}
       (comment: any) =>
         comment.path === path &&
         comment.body !== '' &&
-        ((comment.start_line &&
+        ((comment.start_line !== undefined &&
           comment.start_line >= start_line &&
           comment.line <= end_line) ||
           comment.line === end_line)