ssh: honor core.sshcommand

Callers can specify the ssh command to invoke using `core.sshcommand` or
the `GIT_SSH` environment variable. This is useful for specifying
alternate configuration, and is particularly useful for our testing
environment.

ci/test.sh

@@ -414,6 +414,8 @@ if [ -z "$SKIP_SSH_TESTS" ]; then
 	export GITTEST_REMOTE_SSH_PASSPHRASE=""
 	export GITTEST_REMOTE_SSH_FINGERPRINT="${SSH_FINGERPRINT}"
 
+	export GITTEST_SSH_CMD="ssh -i ${HOME}/.ssh/id_rsa -o UserKnownHostsFile=${HOME}/.ssh/known_hosts"
+
 	echo ""
 	echo "Running ssh tests"
 	echo ""
@@ -430,6 +432,8 @@ if [ -z "$SKIP_SSH_TESTS" ]; then
 	run_test ssh
 	unset GITTEST_REMOTE_URL
 
+	unset GITTEST_SSH_CMD
+
 	unset GITTEST_REMOTE_USER
 	unset GITTEST_REMOTE_SSH_KEY
 	unset GITTEST_REMOTE_SSH_PUBKEY

src/libgit2/transports/ssh.c

@@ -64,6 +64,8 @@ int git_transport_ssh_with_paths(
 
 	*out = transport;
 	return 0;
+#elif GIT_SSH_EXEC
+	abort();
 #else
 	GIT_UNUSED(out);
 	GIT_UNUSED(owner);

src/libgit2/transports/ssh_exec.c

@@ -11,10 +11,12 @@
 
 #include "common.h"
 
+#include "config.h"
 #include "net.h"
 #include "path.h"
 #include "futils.h"
 #include "process.h"
+#include "transports/smart.h"
 
 typedef struct {
 	git_smart_subtransport_stream parent;
@@ -114,17 +116,54 @@ GIT_INLINE(int) ensure_transport_state(
 	return 0;
 }
 
+static int get_ssh_cmdline(
+	git_str *out,
+	ssh_exec_subtransport *transport,
+	git_net_url *url,
+	const char *command)
+{
+	git_remote *remote = ((transport_smart *)transport->owner)->owner;
+	git_repository *repo = remote->repo;
+	git_config *cfg;
+	git_str ssh_cmd = GIT_STR_INIT;
+	const char *default_ssh_cmd = "ssh";
+	int error;
+
+	if ((error = git_repository_config_snapshot(&cfg, repo)) < 0)
+		return error;
+
+	if ((error = git__getenv(&ssh_cmd, "GIT_SSH")) == 0)
+		;
+	else if (error != GIT_ENOTFOUND)
+		goto done;
+	else if ((error = git_config__get_string_buf(&ssh_cmd, cfg, "core.sshcommand")) < 0 && error != GIT_ENOTFOUND)
+		goto done;
+
+	error = git_str_printf(out, "%s -p %s \"%s%s%s\" \"%s\" \"%s\"",
+		ssh_cmd.size > 0 ? ssh_cmd.ptr : default_ssh_cmd,
+		url->port,
+		url->username ? url->username : "",
+		url->username ? "@" : "",
+		url->host,
+		command,
+		url->path);
+
+done:
+	git_str_dispose(&ssh_cmd);
+	git_config_free(cfg);
+	return error;
+}
+
 static int start_ssh(
 	ssh_exec_subtransport *transport,
 	git_smart_service_t action,
 	const char *sshpath)
 {
-	const char *args[6];
 	const char *env[] = { "GIT_DIR=" };
 
 	git_process_options process_opts = GIT_PROCESS_OPTIONS_INIT;
 	git_net_url url = GIT_NET_URL_INIT;
-	git_str userhost = GIT_STR_INIT;
+	git_str ssh_cmdline = GIT_STR_INIT;
 	const char *command;
 	int error;
 
@@ -153,20 +192,11 @@ static int start_ssh(
 	if (error < 0)
 		goto done;
 
-	if (url.username) {
-		git_str_puts(&userhost, url.username);
-		git_str_putc(&userhost, '@');
-	}
-	git_str_puts(&userhost, url.host);
+	if ((error = get_ssh_cmdline(&ssh_cmdline, transport, &url, command)) < 0)
+		goto done;
 
-	args[0] = "/usr/bin/ssh";
-	args[1] = "-p";
-	args[2] = url.port;
-	args[3] = userhost.ptr;
-	args[4] = command;
-	args[5] = url.path;
-
-	if ((error = git_process_new(&transport->process, args, ARRAY_SIZE(args), env, ARRAY_SIZE(env), &process_opts)) < 0 ||
+	if ((error = git_process_new_from_cmdline(&transport->process,
+	     ssh_cmdline.ptr, env, ARRAY_SIZE(env), &process_opts)) < 0 ||
 	    (error = git_process_start(transport->process)) < 0) {
 		git_process_free(transport->process);
 		transport->process = NULL;
@@ -174,7 +204,7 @@ static int start_ssh(
 	}
 
 done:
-	git_str_dispose(&userhost);
+	git_str_dispose(&ssh_cmdline);
 	git_net_url_dispose(&url);
 	return error;
 }

tests/libgit2/online/clone.c

@@ -47,6 +47,9 @@ static char *_orig_http_proxy = NULL;
 static char *_orig_https_proxy = NULL;
 static char *_orig_no_proxy = NULL;
 
+static char *_ssh_cmd = NULL;
+static char *_orig_ssh_cmd = NULL;
+
 static int ssl_cert(git_cert *cert, int valid, const char *host, void *payload)
 {
 	GIT_UNUSED(cert);
@@ -102,6 +105,14 @@ void test_online_clone__initialize(void)
 	_orig_https_proxy = cl_getenv("HTTPS_PROXY");
 	_orig_no_proxy = cl_getenv("NO_PROXY");
 
+	_orig_ssh_cmd = cl_getenv("GIT_SSH");
+	_ssh_cmd = cl_getenv("GITTEST_SSH_CMD");
+
+	if (_ssh_cmd)
+		cl_setenv("GIT_SSH", _ssh_cmd);
+	else
+		cl_setenv("GIT_SSH", NULL);
+
 	if (_remote_expectcontinue)
 		git_libgit2_opts(GIT_OPT_ENABLE_HTTP_EXPECT_CONTINUE, 1);
 }
@@ -149,6 +160,11 @@ void test_online_clone__cleanup(void)
 	git__free(_orig_https_proxy);
 	git__free(_orig_no_proxy);
 
+	cl_setenv("GIT_SSH", _orig_ssh_cmd);
+	git__free(_orig_ssh_cmd);
+
+	git__free(_ssh_cmd);
+
 	git_libgit2_opts(GIT_OPT_SET_SSL_CERT_LOCATIONS, NULL, NULL);
 	git_libgit2_opts(GIT_OPT_SET_SERVER_TIMEOUT, 0);
 	git_libgit2_opts(GIT_OPT_SET_SERVER_CONNECT_TIMEOUT, 0);

tests/libgit2/online/push.c

@@ -20,6 +20,9 @@ static char *_remote_ssh_passphrase = NULL;
 static char *_remote_default = NULL;
 static char *_remote_expectcontinue = NULL;
 
+static char *_orig_ssh_cmd = NULL;
+static char *_ssh_cmd = NULL;
+
 static int cred_acquire_cb(git_credential **,	const char *, const char *, unsigned int, void *);
 
 static git_remote *_remote;
@@ -369,6 +372,14 @@ void test_online_push__initialize(void)
 	_remote_expectcontinue = cl_getenv("GITTEST_REMOTE_EXPECTCONTINUE");
 	_remote = NULL;
 
+	_orig_ssh_cmd = cl_getenv("GIT_SSH");
+	_ssh_cmd = cl_getenv("GITTEST_SSH_CMD");
+
+	if (_ssh_cmd)
+		cl_setenv("GIT_SSH", _ssh_cmd);
+	else
+		cl_setenv("GIT_SSH", NULL);
+
 	/* Skip the test if we're missing the remote URL */
 	if (!_remote_url)
 		cl_skip();
@@ -423,6 +434,9 @@ void test_online_push__cleanup(void)
 	git__free(_remote_default);
 	git__free(_remote_expectcontinue);
 
+	git__free(_orig_ssh_cmd);
+	git__free(_ssh_cmd);
+
 	/* Freed by cl_git_sandbox_cleanup */
 	_repo = NULL;