"git imap-send" did not compile well with older version of cURL library.

* js/imap-send-curl-compilation-fix:
  imap-send: only use CURLOPT_LOGIN_OPTIONS if it is actually available

This fixes the compilation on an older Linux that was used to debug
test failures when upgrading Git for Windows to Git v2.3.0.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

It's a common pattern to do:

  foo = xmalloc(strlen(one) + strlen(two) + 1 + 1);
  sprintf(foo, "%s %s", one, two);

(or possibly some variant with strcpy()s or a more
complicated length computation).  We can switch these to use
xstrfmt, which is shorter, involves less error-prone manual
computation, and removes many sprintf and strcpy calls which
make it harder to audit the code for real buffer overflows.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

If both USE_CURL_FOR_IMAP_SEND and NO_OPENSSL are defined do
not force the user to add --curl to get a working git imap-send
command.

Instead automatically select --curl and warn and ignore the
--no-curl option.  And while we're in there, correct the
warning message when --curl is requested but not supported.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

According to the cURL documentation for the CURLOPT_USE_SSL option,
it is only used with plain text protocols that get upgraded to SSL
using the STARTTLS command.

The server.use_ssl variable is only set when we are using a protocol
that is already SSL/TLS (i.e. imaps), so setting CURLOPT_USE_SSL
when the server.use_ssl variable is set has no effect whatsoever.

Instead, set CURLOPT_USE_SSL to CURLUSESSL_TRY when the server.use_ssl
variable is NOT set so that cURL will attempt to upgrade the plain
text connection to SSL/TLS using STARTTLS in that case.

This much more closely matches the behavior of the non-cURL code path.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

When using git-imap-send to send via cURL, support setting
the GIT_CURL_VERBOSE environment variable to enable cURL's
verbose mode.

The existing http.c code already supports this and does
it by simply checking to see whether or not the environment
variable exists -- it does not examine the value at all.

For consistency, enable CURLOPT_VERBOSE when GIT_CURL_VERBOSE
is set by using the exact same test that http.c does.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Use libcurl's high-level API functions to implement git-imap-send
instead of the previous low-level OpenSSL-based functions.

Since version 7.30.0, libcurl's API has been able to communicate with
IMAP servers. Using those high-level functions instead of the current
ones would reduce imap-send.c by some 1200 lines of code. For now,
the old ones are wrapped in #ifdefs, and the new functions are enabled
by make if curl's version is >= 7.34.0, from which version on curl's
CURLOPT_LOGIN_OPTIONS (enabling IMAP authentication) parameter has been
available. The low-level functions will still be used for tunneling
into the server for now.

As I don't have access to that many IMAP servers, I haven't been able to
test the new code with a wide variety of parameter combinations. I did
test both secure and insecure (imaps:// and imap://) connections and
values of "PLAIN" and "LOGIN" for the authMethod.

In order to suppress a sparse warning about "using sizeof on a
function", we use the same solution used in commit 9371322a6
("sparse: suppress some "using sizeof on a function" warnings",
06-10-2013) which solved exactly this problem for the other commands
using libcurl.

Helped-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Bernhard Reiter <ockham@raz.or.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

The -v/-q options were sort-of supported but without using the
parse-options API, and were not documented.

Signed-off-by: Bernhard Reiter <ockham@raz.or.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Code clean-up.

* as/calloc-takes-nmemb-then-size:
  calloc() and xcalloc() takes nmemb and then size

Code clean-up.

* br/imap-send-simplify-tunnel-child-process:
  imap-send: simplify v_issue_imap_cmd() and get_cmd_result() using starts_with()
  imap-send.c: imap_folder -> imap_server_conf.folder
  git-imap-send: simplify tunnel construction