Close temp file handles before cleanup on Windows

Windows cannot remove files while handles are still open. In
TestOSCommandFileType we created files and immediately called RemoveAll without
closing handles, which left untracked artifacts (e.g. "testFile" and "file with
spaces") in the working tree. Close the handles and assert RemoveAll succeeds so
cleanup failures are visible.

pkg/commands/oscommands/os_test.go

@@ -91,7 +91,11 @@ func TestOSCommandFileType(t *testing.T) {
 		{
 			"testFile",
 			func() {
-				if _, err := os.Create("testFile"); err != nil {
+				f, err := os.Create("testFile")
+				if err != nil {
+					panic(err)
+				}
+				if err := f.Close(); err != nil {
 					panic(err)
 				}
 			},
@@ -102,7 +106,11 @@ func TestOSCommandFileType(t *testing.T) {
 		{
 			"file with spaces",
 			func() {
-				if _, err := os.Create("file with spaces"); err != nil {
+				f, err := os.Create("file with spaces")
+				if err != nil {
+					panic(err)
+				}
+				if err := f.Close(); err != nil {
 					panic(err)
 				}
 			},
@@ -133,7 +141,7 @@ func TestOSCommandFileType(t *testing.T) {
 	for _, s := range scenarios {
 		s.setup()
 		s.test(FileType(s.path))
-		_ = os.RemoveAll(s.path)
+		assert.NoError(t, os.RemoveAll(s.path))
 	}
 }