qemu-ga: adding vss-[un]install options

Existing command line options include '-s install' and '-s uninstall'.
These options install/uninstall both Windows QEMU GA service
and optional VSS COM server. The QEMU GA Windows service allows
always-on serving guest agent's QMP commands and VSS COM server
enables guest agent integration with Volume Shadow Service.

This commit introdices new options '-s vss-install' and '-s vss-uninstall',
affecting only GA VSS COM server registration. The new options are useful
for registering and unregistering the COM server during MSI installation,
upgrade and uninstallation.

Signed-off-by: Yossi Hindin <yhindin@redhat.com>
Message-Id: <1430913460-13174-2-git-send-email-yhindin@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

qga/main.c

@@ -211,7 +211,7 @@ static void usage(const char *cmd)
 "  -V, --version     print version information and exit\n"
 "  -d, --daemonize   become a daemon\n"
 #ifdef _WIN32
-"  -s, --service     service commands: install, uninstall\n"
+"  -s, --service     service commands: install, uninstall, vss-install, vss-uninstall\n"
 #endif
 "  -b, --blacklist   comma-separated list of RPCs to disable (no spaces, \"?\"\n"
 "                    to list available RPCs)\n"
@@ -1036,6 +1036,14 @@ int main(int argc, char **argv)
             } else if (strcmp(service, "uninstall") == 0) {
                 ga_uninstall_vss_provider();
                 return ga_uninstall_service();
+            } else if (strcmp(service, "vss-install") == 0) {
+                if (ga_install_vss_provider()) {
+                    return EXIT_FAILURE;
+                }
+                return EXIT_SUCCESS;
+            } else if (strcmp(service, "vss-uninstall") == 0) {
+                ga_uninstall_vss_provider();
+                return EXIT_SUCCESS;
             } else {
                 printf("Unknown service command.\n");
                 return EXIT_FAILURE;