test,fs: add fs.rm() tests for .git directories

Git for Windows creates read-only files inside the .git directory.
fs.rm() was built in a way, to work around any EPERM error that can
happen while deleting the .git directory by turning the directory
into a writable one. This change adds a regression test for that.

Refs: isaacs/rimraf#21
Refs: nodejs#38810 (comment)
Signed-off-by: Darshan Sen <raisinten@gmail.com>

Author: RaisinTen

test/parallel/test-fs-rm.js

@@ -130,6 +130,17 @@ function removeAsync(dir) {
   }));
 }
 
+// Removing a .git directory should not throw an EPERM.
+// Refs: https://github.com/isaacs/rimraf/issues/21.
+{
+  const gitDirectory = nextDirPath();
+  fs.mkdirSync(gitDirectory);
+  execSync(`git -C ${gitDirectory} init`);
+  fs.rm(gitDirectory, { recursive: true }, common.mustSucceed(() => {
+    assert.strictEqual(fs.existsSync(gitDirectory), false);
+  }));
+}
+
 // Test the synchronous version.
 {
   const dir = nextDirPath();
@@ -179,6 +190,16 @@ function removeAsync(dir) {
   assert.throws(() => fs.rmSync(dir), { syscall: 'stat' });
 }
 
+// Removing a .git directory should not throw an EPERM.
+// Refs: https://github.com/isaacs/rimraf/issues/21.
+{
+  const gitDirectory = nextDirPath();
+  fs.mkdirSync(gitDirectory);
+  execSync(`git -C ${gitDirectory} init`);
+  fs.rmSync(gitDirectory, { recursive: true });
+  assert.strictEqual(fs.existsSync(gitDirectory), false);
+}
+
 // Test the Promises based version.
 (async () => {
   const dir = nextDirPath();
@@ -230,6 +251,16 @@ function removeAsync(dir) {
   }
 })().then(common.mustCall());
 
+// Removing a .git directory should not throw an EPERM.
+// Refs: https://github.com/isaacs/rimraf/issues/21.
+(async () => {
+  const gitDirectory = nextDirPath();
+  fs.mkdirSync(gitDirectory);
+  execSync(`git -C ${gitDirectory} init`);
+  await fs.promises.rm(gitDirectory, { recursive: true });
+  assert.strictEqual(fs.existsSync(gitDirectory), false);
+})().then(common.mustCall());
+
 // Test input validation.
 {
   const dir = nextDirPath();