[RFC 0/3] imap-send curl tunnelling support

From 7.21.5, curl can be tricked into using an open fd. This series uses this to allow using curl over a tunnel.

I have a few doubt on patch #2:
- is socketpair working on all git supported system (windows ?)
- should socketpair always be used or limited to the curl over tunnel case ?
  I don't think there is too much different between an unname pipe and a socketpair but I'm not sure either :)

This series also shows a "bug" in curl. When trying out the tunnel example fro imap-send documentation, this happends: Starting tunnel 'ssh -q -C localhost /usr/sbin/imapd ./Maildir'... ok sending 3 messages 16:38:54.055221 http.c:639 == Info: Hostname was NOT found in DNS cache 16:38:54.059505 http.c:639 == Info: Trying ::1... 16:38:54.059545 http.c:639 == Info: Connected to localhost () port 143 (#0) 16:38:54.354379 http.c:586 <= Recv header, 0000000332 bytes (0x0000014c) 16:38:54.354405 http.c:598 <= Recv header: * PREAUTH [CAPABILITY IMAP4REV1 I18NLEVEL=1 LITERAL+ IDLE UIDPLUS NAMESPACE CHILDREN MAILBOX-REFERRALS BINARY UNSELECT ESEARCH WITHIN SCAN SORT THREAD=REFERENCES THREAD=ORDEREDSUBJECT MULTIAPPEND] Pre-authenticated user nmorey portia.home.nicolas.morey-chaisemartin.com IMAP4rev1 2007e.404 at Wed, 9 Aug 2017 16:38:54 +0200 (CEST) 16:38:54.354425 http.c:639 == Info: Bad tagged response 16:38:54.354448 http.c:639 == Info: Closing connection 0 curl_easy_perform() failed: FTP: weird server reply

It appears curl do not support the PREAUTH tag.

However a test with "nc imap.server.ext 143" is working fine.

Nicolas Morey-Chaisemartin (3):
  imap-send: move tunnel setup to its own function
  imap-send: use a socketpair instead of pipe to communicate with the
    tunnel
  imap_send: add support for curl over tunnel

 Documentation/git-imap-send.txt |  4 +-
 imap-send.c                     | 91 +++++++++++++++++++++++++++++++----------
 2 files changed, 72 insertions(+), 23 deletions(-)