http: check CURLE_SSL_PINNEDPUBKEYNOTMATCH when emitting errors

Change the error shown when a http.pinnedPubKey doesn't match to point
the http.pinnedPubKey variable added in aeff8a61216 (http: implement
public key pinning, 2016-02-15), e.g.:

    git -c http.pinnedPubKey=sha256/someNonMatchingKey ls-remote https://github.com/git/git.git
    fatal: unable to access 'https://github.com/git/git.git/' with http.pinnedPubkey configuration: SSL: public key does not match pinned public key!

Before this we'd emit the exact same thing without the " with
http.pinnedPubkey configuration". The advantage of doing this is that
we're going to get a translated message (everything after the ":" is
hardcoded in English in libcurl), and we've got a reference to the
git-specific configuration variable that's causing the error.

Unfortunately we can't test this easily, as there are no tests that
require https:// in the test suite, and t/lib-httpd.sh doesn't know
how to set up such tests. See [1] for the start of a discussion about
what it would take to have divergent "t/lib-httpd/apache.conf" test
setups. #leftoverbits

1. https://lore.kernel.org/git/YUonS1uoZlZEt+Yd@coredump.intra.peff.net/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/http.c b/http.c
index d7c20493d7..b6735b51c3 100644
--- a/http.c
+++ b/http.c
@@ -1489,6 +1489,10 @@ static int handle_curl_result(struct slot_results *results)
 		 */
 		credential_reject(&cert_auth);
 		return HTTP_NOAUTH;
+#ifdef GIT_CURL_HAVE_CURLE_SSL_PINNEDPUBKEYNOTMATCH
+	} else if (results->curl_result == CURLE_SSL_PINNEDPUBKEYNOTMATCH) {
+		return HTTP_NOMATCHPUBLICKEY;
+#endif
 	} else if (missing_target(results))
 		return HTTP_MISSING_TARGET;
 	else if (results->http_code == 401) {