Table operating commands. (#1686)

* Table operating commands.

* Updated merge test for clarity.

* More clarity.

* Better like this..

crates/nu-cli/tests/commands/keep_while.rs

@@ -0,0 +1,51 @@
+use nu_test_support::fs::Stub::FileWithContentToBeTrimmed;
+use nu_test_support::playground::Playground;
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn condition_is_met() {
+    Playground::setup("keep-while_test_1", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContentToBeTrimmed(
+            "caballeros.txt",
+            r#"
+                CHICKEN SUMMARY                        report date: April 29th, 2020
+                --------------------------------------------------------------------
+                Chicken Collection,29/04/2020,30/04/2020,31/04/2020,
+                Yellow Chickens,,,
+                Andrés,1,1,1
+                Jonathan,1,1,1
+                Jason,1,1,1
+                Yehuda,1,1,1
+                Blue Chickens,,,
+                Andrés,1,1,2
+                Jonathan,1,1,2
+                Jason,1,1,2
+                Yehuda,1,1,2
+                Red Chickens,,,
+                Andrés,1,1,3
+                Jonathan,1,1,3
+                Jason,1,1,3
+                Yehuda,1,1,3
+            "#,
+        )]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                open --raw caballeros.txt
+                | lines
+                | skip 2
+                | split-column ','
+                | headers
+                | skip 1
+                | keep-while "Chicken Collection" != "Blue Chickens"
+                | str "31/04/2020" --to-int
+                | get "31/04/2020"
+                | sum
+                | echo $it
+                "#
+        ));
+
+        assert_eq!(actual, "4");
+    })
+}