fix(ignore-generator): dedupe anchored .gitignore patterns against defaults and skip negation patterns in suggestions

understand-anything-plugin/packages/core/src/__tests__/ignore-generator.test.ts

@@ -158,5 +158,56 @@ describe("generateStarterIgnoreFile", () => {
       const lines = content.split("\n").filter((l) => l.trim() && !l.startsWith("#"));
       expect(lines).toHaveLength(0);
     });
+
+    it("treats anchored .gitignore patterns as covered by defaults", () => {
+      writeFileSync(join(testDir, ".gitignore"), "/node_modules\n/dist\n.env\n");
+      const content = generateStarterIgnoreFile(testDir);
+      // Extract the pattern lines under the .gitignore section (between its
+      // header and the next "# ---" section header).
+      const lines = content.split("\n");
+      const headerIdx = lines.findIndex((l) => l.includes("From .gitignore"));
+      // Guard: if the section were fully deduped, findIndex returns -1 and the
+      // slice below would silently scan from the top of the file (masking a
+      // regression). Assert the section is actually present before slicing.
+      expect(headerIdx).toBeGreaterThanOrEqual(0);
+      const nextSectionIdx = lines.findIndex((l, i) => i > headerIdx && l.startsWith("# ---"));
+      const sectionLines = lines.slice(headerIdx + 1, nextSectionIdx === -1 ? undefined : nextSectionIdx);
+      const patterns = sectionLines
+        .filter((l) => l.startsWith("# ") && !l.startsWith("# ---"))
+        .map((l) => l.slice(2));
+      // /node_modules and /dist are anchored forms of defaults node_modules/ and dist/.
+      expect(patterns).not.toContain("/node_modules"); // fails today: '# /node_modules' is present
+      expect(patterns).not.toContain("/dist"); // fails today: '# /dist' is present
+      expect(patterns).toContain(".env"); // still suggested
+    });
+
+    it("treats **/ and ./ anchor variants as covered by defaults", () => {
+      writeFileSync(
+        join(testDir, ".gitignore"),
+        "**/node_modules\n**/build/\n./dist/\n.env\n",
+      );
+      const content = generateStarterIgnoreFile(testDir);
+      const lines = content.split("\n");
+      const headerIdx = lines.findIndex((l) => l.includes("From .gitignore"));
+      expect(headerIdx).toBeGreaterThanOrEqual(0);
+      const nextSectionIdx = lines.findIndex((l, i) => i > headerIdx && l.startsWith("# ---"));
+      const sectionLines = lines.slice(headerIdx + 1, nextSectionIdx === -1 ? undefined : nextSectionIdx);
+      const patterns = sectionLines
+        .filter((l) => l.startsWith("# ") && !l.startsWith("# ---"))
+        .map((l) => l.slice(2));
+      // **/node_modules, **/build/, and ./dist/ are anchor variants of defaults.
+      expect(patterns).not.toContain("**/node_modules");
+      expect(patterns).not.toContain("**/build/");
+      expect(patterns).not.toContain("./dist/");
+      // A non-default pattern still survives.
+      expect(patterns).toContain(".env");
+    });
+
+    it("does not suggest .gitignore negation (!) patterns", () => {
+      writeFileSync(join(testDir, ".gitignore"), "build/\n!build/keep.txt\n.env\n");
+      const content = generateStarterIgnoreFile(testDir);
+      expect(content).not.toContain("!build/keep.txt"); // fails today: '# !build/keep.txt' is emitted
+      expect(content).toContain("# .env");
+    });
   });
 });

understand-anything-plugin/packages/core/src/ignore-generator.ts

@@ -33,22 +33,37 @@ const GENERIC_SUGGESTIONS = [
 
 /**
  * Parses a .gitignore file and returns active patterns (no comments, no blanks).
+ *
+ * Negation (`!`) lines are intentionally dropped: a `!pattern` force-INCLUDES a
+ * path and is only meaningful relative to the project's own .gitignore ignore
+ * stack, which understand-anything does not apply. Surfacing it under the
+ * "uncomment to exclude" suggestion section would invert its semantics, so it is
+ * omitted rather than presented as a candidate exclusion. The header still
+ * documents the general `!` mechanism for users who want to author one by hand.
  */
 function parseGitignorePatterns(gitignorePath: string): string[] {
   if (!existsSync(gitignorePath)) return [];
   const content = readFileSync(gitignorePath, "utf-8");
   return content
     .split("\n")
     .map((line) => line.trim())
-    .filter((line) => line.length > 0 && !line.startsWith("#"));
+    .filter(
+      (line) => line.length > 0 && !line.startsWith("#") && !line.startsWith("!"),
+    );
 }
 
 /**
  * Returns true if a gitignore pattern is already covered by the hardcoded defaults.
- * Normalizes trailing slashes for comparison.
+ * Normalizes leading anchors (root "/", "./", and globstar) and trailing slashes
+ * for comparison so that anchored forms like `/node_modules`, `./dist/`, and a
+ * leading globstar `node_modules` match the defaults `node_modules/`, `dist/`.
  */
 function isCoveredByDefaults(pattern: string): boolean {
-  const normalize = (p: string) => p.replace(/\/+$/, "");
+  const normalize = (p: string) =>
+    p
+      .replace(/^\.?\/+/, "")
+      .replace(/^\*\*\/+/, "")
+      .replace(/\/+$/, "");
   const normalized = normalize(pattern);
   return DEFAULT_IGNORE_PATTERNS.some((d) => normalize(d) === normalized);
 }