Stub out gpg-migrate.py

Following the general approach outlined by Atom Smasher [1], but I'll
just parse the packets directly in Python.

[1]: http://atom.smasher.org/gpg/gpg-migrate.txt

diff --git a/gpg-migrate.py b/gpg-migrate.py
new file mode 100755 (executable)
index 0000000..e6f1f38
--- /dev/null
+++ b/gpg-migrate.py
@@ -0,0 +1,53 @@
+#!/usr/bin/python
+
+import subprocess as _subprocess
+import struct as _struct
+
+
+def _get_stdout(args, stdin=None):
+    stdin_pipe = None
+    if stdin is not None:
+        stdin_pipe = _subprocess.PIPE
+    p = _subprocess.Popen(args, stdin=stdin_pipe, stdout=_subprocess.PIPE)
+    stdout, stderr = p.communicate(stdin)
+    status = p.wait()
+    if status != 0:
+        raise RuntimeError(status)
+    return stdout
+
+
+class PGPPacket (dict):
+    # http://tools.ietf.org/search/rfc4880
+    def from_bytes(self, data):
+        pass
+
+    def to_bytes(self):
+        pass
+
+
+def migrate(old_key, new_key):
+    """Add the old key and sub-keys to the new key
+
+    For example, to upgrade your master key, while preserving old
+    signatures you'd made.  You will lose signature *on* your old key
+    though, since sub-keys can't be signed (I don't think).
+    """
+    old_key_export = _get_stdout(
+        ['gpg', '--export', old_key])
+    old_key_packet = PGPPacket()
+    old_key_packet.from_bytes(data=old_key_export)
+    old_key_secret_export = _get_stdout(
+        ['gpg', '--export-secret-keys', old_key])
+    old_key_secret_packet = PGPPacket()
+    old_key_secret_packet.from_bytes(data=old_key_secret_export)
+
+    import pprint
+    pprint.pprint(old_key_packet)
+    pprint.pprint(old_key_secret_packet)
+
+
+if __name__ == '__main__':
+    import sys as _sys
+
+    old_key, new_key = _sys.argv[1:3]
+    migrate(old_key=old_key, new_key=new_key)