separate commandline into subcommands (#11877)

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# Description
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Related issue and PR, #11825 #11864 
This improves the signature of `commandline`.

## Before

`commandline` returns different types depending on the flags and an
aurgument.

| command | input | output | description |

|-----------------------------|---------|---------|----------------------------------------|
| `commandline` | nothing | string | get current cursor line |
| `commandline arg` | nothing | nothing | replace the cursor line with
`arg` |
| `commandline --append arg` | nothing | nothing | append `arg` to the
end of cursor line |
| `commandline --insert arg` | nothing | nothing | insert `arg` to the
position of cursor |
| `commandline --replace arg` | nothing | nothing | replace the cursor
line with `arg` |
| `commandline --cursor` | nothing | int | get current cursor position |
| `commandline --cursor pos` | nothing | nothing | set cursor position
to pos |
| `commandline --cursor-end` | nothing | nothing | set cursor position
to end |

`help commandline` shows that `commandline` accepts string as pipeline
input, but `commandline` ignores pipeline input.

```
Input/output types:
  ╭───┬─────────┬─────────╮
  │ # │  input  │ output  │
  ├───┼─────────┼─────────┤
  │ 0 │ nothing │ nothing │
  │ 1 │ string  │ string  │
  ╰───┴─────────┴─────────╯
```

671bd08bcd/crates/nu-cli/src/commands/commandline.rs (L70)

This is misleading.

Due to the change #11864 , typecheck does not work well.
https://github.com/nushell/nushell/pull/11864#discussion_r1491814054

## After

Separate `commandline` into subcommands so that each subcommands returns
the same type for the same input type.

| command | input | output | description |

|----------------------------------|---------|---------|----------------------------------------|
| `commandline` | nothing | string | get current cursor line |
| `commandline edit arg` | nothing | nothing | replace the cursor line
with `arg` |
| `commandline edit --append arg` | nothing | nothing | append `arg` to
the end of cursor line |
| `commandline edit --insert arg` | nothing | nothing | insert `arg` to
the position of cursor |
| `commandline edit --replace arg` | nothing | nothing | replace the
cursor line with `arg` |
| `commandline get-cursor` | nothing | int | get current cursor position
|
| `commandline set-cursor pos` | nothing | nothing | set cursor position
to pos |
| `commandline set-cursor --end` | nothing | nothing | set cursor
position to end |

# User-Facing Changes
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src/tests/test_commandline.rs

@@ -1,4 +1,5 @@
 use crate::tests::{fail_test, run_test, TestResult};
+use nu_test_support::nu;
 
 #[test]
 fn commandline_test_get_empty() -> TestResult {
@@ -7,6 +8,142 @@ fn commandline_test_get_empty() -> TestResult {
 
 #[test]
 fn commandline_test_append() -> TestResult {
+    run_test(
+        "commandline edit --replace '0👩‍❤️‍👩2'\n\
+        commandline set-cursor 2\n\
+        commandline edit --append 'ab'\n\
+        print (commandline)\n\
+        commandline get-cursor",
+        "0👩‍❤️‍👩2ab\n\
+        2",
+    )
+}
+
+#[test]
+fn commandline_test_insert() -> TestResult {
+    run_test(
+        "commandline edit --replace '0👩‍❤️‍👩2'\n\
+        commandline set-cursor 2\n\
+        commandline edit --insert 'ab'\n\
+        print (commandline)\n\
+        commandline get-cursor",
+        "0👩‍❤️‍👩ab2\n\
+        4",
+    )
+}
+
+#[test]
+fn commandline_test_replace() -> TestResult {
+    run_test(
+        "commandline edit --replace '0👩‍❤️‍👩2'\n\
+        commandline edit --replace 'ab'\n\
+        print (commandline)\n\
+        commandline get-cursor",
+        "ab\n\
+        2",
+    )
+}
+
+#[test]
+fn commandline_test_cursor() -> TestResult {
+    run_test(
+        "commandline edit --replace '0👩‍❤️‍👩2'\n\
+        commandline set-cursor 1\n\
+        commandline edit --insert 'x'\n\
+        commandline",
+        "0x👩‍❤️‍👩2",
+    )?;
+    run_test(
+        "commandline edit --replace '0👩‍❤️‍👩2'\n\
+        commandline set-cursor 2\n\
+        commandline edit --insert 'x'\n\
+        commandline",
+        "0👩‍❤️‍👩x2",
+    )
+}
+
+#[test]
+fn commandline_test_cursor_show_pos_begin() -> TestResult {
+    run_test(
+        "commandline edit --replace '0👩‍❤️‍👩'\n\
+        commandline set-cursor 0\n\
+        commandline get-cursor",
+        "0",
+    )
+}
+
+#[test]
+fn commandline_test_cursor_show_pos_end() -> TestResult {
+    run_test(
+        "commandline edit --replace '0👩‍❤️‍👩'\n\
+        commandline set-cursor 2\n\
+        commandline get-cursor",
+        "2",
+    )
+}
+
+#[test]
+fn commandline_test_cursor_show_pos_mid() -> TestResult {
+    run_test(
+        "commandline edit --replace '0👩‍❤️‍👩2'\n\
+        commandline set-cursor 1\n\
+        commandline get-cursor",
+        "1",
+    )?;
+    run_test(
+        "commandline edit --replace '0👩‍❤️‍👩2'\n\
+        commandline set-cursor 2\n\
+        commandline get-cursor",
+        "2",
+    )
+}
+
+#[test]
+fn commandline_test_cursor_too_small() -> TestResult {
+    run_test(
+        "commandline edit --replace '123456'\n\
+        commandline set-cursor -1\n\
+        commandline edit --insert '0'\n\
+        commandline",
+        "0123456",
+    )
+}
+
+#[test]
+fn commandline_test_cursor_too_large() -> TestResult {
+    run_test(
+        "commandline edit --replace '123456'\n\
+        commandline set-cursor 10\n\
+        commandline edit --insert '0'\n\
+        commandline",
+        "1234560",
+    )
+}
+
+#[test]
+fn commandline_test_cursor_invalid() -> TestResult {
+    fail_test(
+        "commandline edit --replace '123456'\n\
+        commandline set-cursor 'abc'",
+        "expected int",
+    )
+}
+
+#[test]
+fn commandline_test_cursor_end() -> TestResult {
+    run_test(
+        "commandline edit --insert '🤔🤔'; commandline set-cursor --end; commandline get-cursor",
+        "2", // 2 graphemes
+    )
+}
+
+#[test]
+fn commandline_test_cursor_type() -> TestResult {
+    run_test("commandline get-cursor | describe", "int")
+}
+
+#[test]
+fn deprecated_commandline_test_append() -> TestResult {
     run_test(
         "commandline --replace '0👩‍❤️‍👩2'\n\
         commandline --cursor '2'\n\
@@ -19,7 +156,7 @@ fn commandline_test_append() -> TestResult {
 }
 
 #[test]
-fn commandline_test_insert() -> TestResult {
+fn deprecated_commandline_test_insert() -> TestResult {
     run_test(
         "commandline --replace '0👩‍❤️‍👩2'\n\
         commandline --cursor '2'\n\
@@ -32,7 +169,7 @@ fn commandline_test_insert() -> TestResult {
 }
 
 #[test]
-fn commandline_test_replace() -> TestResult {
+fn deprecated_commandline_test_replace() -> TestResult {
     run_test(
         "commandline --replace '0👩‍❤️‍👩2'\n\
         commandline --replace 'ab'\n\
@@ -44,7 +181,7 @@ fn commandline_test_replace() -> TestResult {
 }
 
 #[test]
-fn commandline_test_cursor() -> TestResult {
+fn deprecated_commandline_test_cursor() -> TestResult {
     run_test(
         "commandline --replace '0👩‍❤️‍👩2'\n\
         commandline --cursor '1'\n\
@@ -62,7 +199,7 @@ fn commandline_test_cursor() -> TestResult {
 }
 
 #[test]
-fn commandline_test_cursor_show_pos_begin() -> TestResult {
+fn deprecated_commandline_test_cursor_show_pos_begin() -> TestResult {
     run_test(
         "commandline --replace '0👩‍❤️‍👩'\n\
         commandline --cursor '0'\n\
@@ -72,7 +209,7 @@ fn commandline_test_cursor_show_pos_begin() -> TestResult {
 }
 
 #[test]
-fn commandline_test_cursor_show_pos_end() -> TestResult {
+fn deprecated_commandline_test_cursor_show_pos_end() -> TestResult {
     run_test(
         "commandline --replace '0👩‍❤️‍👩'\n\
         commandline --cursor '2'\n\
@@ -82,7 +219,7 @@ fn commandline_test_cursor_show_pos_end() -> TestResult {
 }
 
 #[test]
-fn commandline_test_cursor_show_pos_mid() -> TestResult {
+fn deprecated_commandline_test_cursor_show_pos_mid() -> TestResult {
     run_test(
         "commandline --replace '0👩‍❤️‍👩2'\n\
         commandline --cursor '1'\n\
@@ -98,7 +235,7 @@ fn commandline_test_cursor_show_pos_mid() -> TestResult {
 }
 
 #[test]
-fn commandline_test_cursor_too_small() -> TestResult {
+fn deprecated_commandline_test_cursor_too_small() -> TestResult {
     run_test(
         "commandline --replace '123456'\n\
         commandline --cursor '-1'\n\
@@ -109,7 +246,7 @@ fn commandline_test_cursor_too_small() -> TestResult {
 }
 
 #[test]
-fn commandline_test_cursor_too_large() -> TestResult {
+fn deprecated_commandline_test_cursor_too_large() -> TestResult {
     run_test(
         "commandline --replace '123456'\n\
         commandline --cursor '10'\n\
@@ -120,7 +257,7 @@ fn commandline_test_cursor_too_large() -> TestResult {
 }
 
 #[test]
-fn commandline_test_cursor_invalid() -> TestResult {
+fn deprecated_commandline_test_cursor_invalid() -> TestResult {
     fail_test(
         "commandline --replace '123456'\n\
         commandline --cursor 'abc'",
@@ -129,7 +266,7 @@ fn commandline_test_cursor_invalid() -> TestResult {
 }
 
 #[test]
-fn commandline_test_cursor_end() -> TestResult {
+fn deprecated_commandline_test_cursor_end() -> TestResult {
     run_test(
         "commandline --insert '🤔🤔'; commandline --cursor-end; commandline --cursor",
         "2", // 2 graphemes
@@ -137,6 +274,43 @@ fn commandline_test_cursor_end() -> TestResult {
 }
 
 #[test]
-fn commandline_test_cursor_type() -> TestResult {
-    run_test("commandline --cursor | describe", "int")
+fn deprecated_commandline_flag_cursor_get() {
+    let actual = nu!("commandline --cursor");
+    assert!(actual.err.contains("deprecated"));
+}
+
+#[test]
+fn deprecated_commandline_flag_cursor_set() {
+    let actual = nu!("commandline -c 0");
+    assert!(actual.err.contains("deprecated"));
+}
+
+#[test]
+fn deprecated_commandline_flag_cursor_end() {
+    let actual = nu!("commandline --cursor-end");
+    assert!(actual.err.contains("deprecated"));
+}
+
+#[test]
+fn deprecated_commandline_flag_append() {
+    let actual = nu!("commandline --append 'abc'");
+    assert!(actual.err.contains("deprecated"));
+}
+
+#[test]
+fn deprecated_commandline_flag_insert() {
+    let actual = nu!("commandline --insert 'abc'");
+    assert!(actual.err.contains("deprecated"));
+}
+
+#[test]
+fn deprecated_commandline_flag_replace() {
+    let actual = nu!("commandline --replace 'abc'");
+    assert!(actual.err.contains("deprecated"));
+}
+
+#[test]
+fn deprecated_commandline_replace_current_buffer() {
+    let actual = nu!("commandline 'abc'");
+    assert!(actual.err.contains("deprecated"));
 }