feat: add --fastsync-server-path flag to configure remote server binary path

src/client/client_cli.c

@@ -56,6 +56,8 @@ static void print_usage(void) {
   printf("  --key <path>        TLS private key file (PEM)\n");
   printf("  --ca <path>         TLS CA certificate file (PEM)\n");
   printf("  --partial           Keep partial files on interrupted transfer\n");
+  printf("  --fastsync-server-path <path>\n");
+  printf("                      Path to fastsync-server on remote (default: fastsync-server)\n");
   printf("  --help              Show this help\n");
   printf("  -V, --version       Show version and exit\n");
 }
@@ -224,6 +226,9 @@ int main(int argc, char* argv[]) {
       config->tls_ca = str_dup(argv[++i]);
     } else if (strcmp(argv[i], "--partial") == 0) {
       config->partial = true;
+    } else if (strcmp(argv[i], "--fastsync-server-path") == 0 && i + 1 < argc) {
+      free(config->fastsync_server_path);
+      config->fastsync_server_path = str_dup(argv[++i]);
     } else if (strcmp(argv[i], "-v") == 0 || strcmp(argv[i], "--verbose") == 0) {
       set_log_level(LOG_LEVEL_DEBUG);
     } else if (argv[i][0] == '-') {

src/client/client_send.c

@@ -228,7 +228,8 @@ static int send_chunks_multithreaded(void* pipeline_context) {
       fprintf(stderr, "Error: -f/--sendfile is not supported with SSH transport\n");
       return 1;
     }
-    client = client_connect_ssh(context->config->ssh_destination, context->config->ssh_port);
+    client = client_connect_ssh(context->config->ssh_destination, context->config->ssh_port,
+                                context->config->fastsync_server_path);
   } else if (context->config->use_tls) {
     client = client_create();
     if (!client || !client_connect_tls(client, context->config->server_host,
@@ -385,7 +386,8 @@ int send_files(Config* config) {
       fprintf(stderr, "Error: -f/--sendfile is not supported with SSH transport\n");
       return 1;
     }
-    client = client_connect_ssh(config->ssh_destination, config->ssh_port);
+    client = client_connect_ssh(config->ssh_destination, config->ssh_port,
+                                config->fastsync_server_path);
     if (!client)
       return 1;
   } else if (config->use_tls) {

src/shared/config.c

@@ -34,6 +34,7 @@ Config* config_create(char* version, char* send_directory, char* receive_directo
   config->ssh_port = 22;
   config->transport = TRANSPORT_TCP;
   config->ssh_destination = NULL;
+  config->fastsync_server_path = NULL;
   config->exclude_patterns = NULL;
   config->exclude_count = 0;
   config->include_patterns = NULL;
@@ -88,6 +89,7 @@ void config_delete(Config* config) {
   free(config->send_directory);
   free(config->receive_root_directory);
   free(config->ssh_destination);
+  free(config->fastsync_server_path);
   for (int i = 0; i < config->exclude_count; i++)
     free(config->exclude_patterns[i]);
   free(config->exclude_patterns);
@@ -238,6 +240,7 @@ Config* config_receive(int file_descriptor) {
   config->ssh_port = 22;
   config->transport = TRANSPORT_TCP;
   config->ssh_destination = NULL;
+  config->fastsync_server_path = NULL;
   config->exclude_patterns = NULL;
   config->exclude_count = 0;
   config->include_patterns = NULL;

src/shared/config.h

@@ -24,6 +24,7 @@ typedef struct Config {
   int ssh_port;
   TransportType transport;
   char* ssh_destination;
+  char* fastsync_server_path;
   char** exclude_patterns;
   int exclude_count;
   char** include_patterns;

src/shared/transport_ssh.c

@@ -67,7 +67,7 @@ static int parse_remote_dest(const char* dest, RemoteDest* r) {
   return 0;
 }
 
-Client* client_connect_ssh(const char* destination, int port) {
+Client* client_connect_ssh(const char* destination, int port, const char* server_path) {
   RemoteDest r;
   if (parse_remote_dest(destination, &r) != 0) {
     fprintf(stderr, "Invalid remote destination: %s\n", destination);
@@ -152,7 +152,7 @@ Client* client_connect_ssh(const char* destination, int port) {
       _exit(1);
     }
     ssh_argv[ac++] = ssh_user;
-    ssh_argv[ac++] = "fastsync-server";
+    ssh_argv[ac++] = (char*)(server_path ? server_path : "fastsync-server");
     ssh_argv[ac++] = "--stdio";
     ssh_argv[ac] = NULL;
     execvp("ssh", ssh_argv);
@@ -174,7 +174,7 @@ Client* client_connect_ssh(const char* destination, int port) {
     close(sv[0]);
     waitpid(pid, NULL, 0);
     remote_dest_destroy(&r);
-    fprintf(stderr, "Error: could not launch 'fastsync-server --stdio' on remote\n");
+    fprintf(stderr, "Error: could not launch '%s --stdio' on remote\n", server_path ? server_path : "fastsync-server");
     return NULL;
   }
 

src/shared/transport_ssh.h

@@ -3,6 +3,6 @@
 
 #include "transport_tcp.h"
 
-Client* client_connect_ssh(const char* destination, int port);
+Client* client_connect_ssh(const char* destination, int port, const char* server_path);
 
 #endif

tests/test_transport_ssh.c

@@ -9,14 +9,14 @@
 static void test_ssh_connect_invalid_dest() {
   /* Missing colon — parse_remote_dest should fail and return NULL */
   /* cppcheck-suppress constVariablePointer */
-  Client* client = client_connect_ssh("invalid-destination-no-colon", 22);
+  Client* client = client_connect_ssh("invalid-destination-no-colon", 22, NULL);
   EXPECT_NULL(client);
 }
 
 /* Test client_connect_ssh with empty destination */
 static void test_ssh_connect_empty_dest() {
   /* cppcheck-suppress constVariablePointer */
-  Client* client = client_connect_ssh("", 22);
+  Client* client = client_connect_ssh("", 22, NULL);
   EXPECT_NULL(client);
 }
 
@@ -24,7 +24,7 @@ static void test_ssh_connect_empty_dest() {
  * parse_remote_dest succeeds, ssh is exec'd and fails, but the function
  * creates a Client that must be cleaned up. */
 static void test_ssh_connect_malformed() {
-  Client* client = client_connect_ssh(":", 22);
+  Client* client = client_connect_ssh(":", 22, NULL);
   /* ssh binary exists, so exec succeeds; the function returns a Client.
    * We just verify it doesn't crash and clean up properly. */
   if (client != NULL) {
@@ -37,7 +37,7 @@ static void test_ssh_connect_malformed() {
 /* Test client_connect_ssh with valid format but unreachable host.
  * The function launches ssh which will fail to connect, returns a Client. */
 static void test_ssh_connect_unreachable() {
-  Client* client = client_connect_ssh("nonexistent.invalid:/remote/path", 22);
+  Client* client = client_connect_ssh("nonexistent.invalid:/remote/path", 22, NULL);
   if (client != NULL) {
     client_disconnect(client);
     client_delete(client);