Add CLI Flag for --forced-separate

Implements #2366

Author: hirak99

docs/configuration/options.md

@@ -499,7 +499,10 @@ Force certain sub modules to show separately
 **Default:** `()`  
 **Config default:** `[]`  
 **Python & Config File Name:** forced_separate  
-**CLI Flags:** **Not Supported**
+**CLI Flags:**
+
+- --fs
+- --forced-separate
 
 **Examples:**
 

isort/main.py

@@ -503,6 +503,14 @@ def _build_arg_parser() -> argparse.ArgumentParser:
         "to be grid wrapped regardless of line "
         "length. If 0 is passed in (the global default) only line length is considered.",
     )
+    output_group.add_argument(
+        "--fs",
+        "--forced-separate",
+        dest="forced_separate",
+        action="append",
+        help="Force specified sub modules to show separately. To specify multiple modules, "
+        "use the argument multiple times: --forced-separate typing --forced-separate six.",
+    )
     output_group.add_argument(
         "-i",
         "--indent",