'guix copy --from' now reports messages much more useful than "failed to
retrieve files".
* guix/ssh.scm (store-export-channel)[export]: Wrap 'use-modules' in
'catch' and 'with-store' in 'guard'. Check for invalid items. Write a
status sexp on stdout.
(raise-error): New macro.
(retrieve-files): Read the initial status sexp and report errors
accordingly.
Fixes <http://bugs.gnu.org/26972>.
* guix/ssh.scm (store-import-channel)[import]: Add 'consume-input'
procedure. Wrap body in 'catch' and 'guard'. Use 'open-remote-pipe'
with OPEN_BOTH instead of 'open-remote-output-pipe'.
(send-files): After the 'channel-send-eof' call, do (read port).
Interpret the result sexp and raise an error condition if needed.
* guix/scripts/offload.scm (connect-to-remote-daemon)
(store-import-channel, store-export-channel, send-files)
(retrieve-files): Move to (guix ssh).
(nonce): Add optional 'name' parameter and use it.
(retrieve-files*): New procedure.
(transfer-and-offload): Use it instead of 'retrieve-files', and add
first parameter to 'send-files'.
(assert-node-can-import): Likewise.
(assert-node-can-export): Use 'retrieve-files' instead of
'store-export-channel'.
* guix/ssh.scm: New file.
* configure.ac: Use 'GUIX_CHECK_GUILE_SSH' and define 'HAVE_GUILE_SSH'
Automake conditional.
* Makefile.am (MODULES) [HAVE_GUILE_SSH]: Add guix/ssh.scm.
Ludovic Courtès