Start work on completion for ssh kitten

kittens/ssh/completion.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+# License: GPLv3 Copyright: 2021, Kovid Goyal <kovid at kovidgoyal.net>
+
+import os
+import subprocess
+from typing import Dict, Iterator, Tuple
+from kitty.types import run_once
+
+
+def iter_known_hosts() -> Iterator[str]:
+    try:
+        f = open(os.path.expanduser('~/.ssh/config'))
+    except OSError:
+        pass
+    else:
+        for line in f:
+            parts = line.split()
+            if parts and parts[0] == 'Host' and len(parts) > 1:
+                yield parts[1]
+
+    try:
+        f = open(os.path.expanduser('~/.ssh/known_hosts'))
+    except OSError:
+        pass
+    else:
+        for line in f:
+            parts = line.split()
+            if parts:
+                yield parts[0]
+
+
+@run_once
+def known_hosts() -> Tuple[str, ...]:
+    return tuple(iter_known_hosts())
+
+
+@run_once
+def ssh_options() -> Dict[str, str]:
+    stderr = subprocess.Popen(['ssh'], stderr=subprocess.PIPE).stderr
+    assert stderr is not None
+    raw = stderr.read().decode('utf-8')
+    ans: Dict[str, str] = {}
+    pos = 0
+    while True:
+        pos = raw.find('[', pos)
+        if pos < 0:
+            break
+        num = 1
+        epos = pos
+        while num > 0:
+            epos += 1
+            if raw[epos] not in '[]':
+                continue
+            num += 1 if raw[epos] == '[' else -1
+        q = raw[pos+1:epos]
+        pos = epos
+        if len(q) < 2 or q[0] != '-':
+            continue
+        if ' ' in q:
+            opt, desc = q.split(' ', 1)
+            ans[opt[1:]] = desc
+        else:
+            ans.update(dict.fromkeys(q[1:], ''))
+    return ans