commit 70020247d1903c7a1262d967cf205a44dc6f6ebe
Author: Keno Fischer <kfischer@college.harvard.edu>
Date:   Wed Jul 20 19:59:00 2016 -0400

    Make failure to connect to ssh-agent non-fatal

    Julia issue: https://github.com/JuliaLang/julia/pull/17459
    Upstream: https://github.com/libgit2/libgit2/issues/3866

diff --git a/src/transports/ssh.c b/src/transports/ssh.c
index cfd5736..82d2c63 100644
--- a/src/transports/ssh.c
+++ b/src/transports/ssh.c
@@ -296,8 +296,10 @@ static int ssh_agent_auth(LIBSSH2_SESSION *session, git_cred_ssh_key *c) {
 
 	rc = libssh2_agent_connect(agent);
 
-	if (rc != LIBSSH2_ERROR_NONE)
+	if (rc != LIBSSH2_ERROR_NONE) {
+		rc = LIBSSH2_ERROR_AUTHENTICATION_FAILED;
 		goto shutdown;
+	}
 
 	rc = libssh2_agent_list_identities(agent);