tr: add squeeze option

tests/test_tr.rs

@@ -32,3 +32,28 @@ fn test_delete_complement() {
     new_ucmd!()
         .args(&["-d", "-c", "a-z"]).pipe_in("aBcD").run().stdout_is("ac");
 }
+
+#[test]
+fn test_squeeze() {
+    new_ucmd!()
+        .args(&["-s", "a-z"]).pipe_in("aaBBcDcc").run().stdout_is("aBBcDc");
+}
+
+
+#[test]
+fn test_squeeze_complement() {
+    new_ucmd!()
+        .args(&["-sc", "a-z"]).pipe_in("aaBBcDcc").run().stdout_is("aaBcDcc");
+}
+
+#[test]
+fn test_delete_and_squeeze() {
+    new_ucmd!()
+        .args(&["-ds", "a-z", "A-Z"]).pipe_in("abBcB").run().stdout_is("B");
+}
+
+#[test]
+fn test_delete_and_squeeze_complement() {
+    new_ucmd!()
+        .args(&["-dsc", "a-z", "A-Z"]).pipe_in("abBcB").run().stdout_is("abc");
+}