Start work on SSH askpass implementation

shell-integration/ssh/askpass.py

@@ -0,0 +1,24 @@
+#!/usr/bin/env -S kitty +launch
+# License: GPLv3 Copyright: 2022, Kovid Goyal <kovid at kovidgoyal.net>
+
+import json
+import os
+import struct
+import sys
+
+from kitty.shm import SharedMemory
+
+msg = sys.argv[-1]
+prompt = os.environ.get('SSH_ASKPASS_PROMPT', '')
+is_confirm = prompt == 'confirm'
+ask_cmdline = ['-m', msg, '--type', 'yesno' if is_confirm else 'password']
+if is_confirm:
+    ask_cmdline += ['--default', 'y']
+data = json.dumps(ask_cmdline).encode('utf-8')
+sz = struct.pack('>I', len(data))
+with SharedMemory(size=len(data) + len(sz) + 1, unlink_on_exit=True, prefix=f'askpass-{os.getpid()}-') as shm, open(os.ctermid(), 'wb') as tty:
+    shm.write(b'\0')
+    shm.write(sz)
+    shm.write(data)
+    shm.flush()
+    print(f'\x1bP@kitty-ask|{shm.name}\x1b\\', flush=True)