Add option --ignore-permissions

On certain file systems, the permissions are limited or fixed. Add
option so that cmirror does not attempt to fix the target file
permissons.

cmirror.c

@@ -289,6 +289,7 @@ static int opt_nice;
 static int unix_socket;
 static char *unix_socket_name;
 static int noatime;
+static int ignore_permissions;
 
 /* globals */
 
@@ -457,7 +458,7 @@ static void check_perm(FileInfo *is, FileInfo *want) {
             warn("chown %d:%d %s\n", want->uid, want->gid, is->name);
         fileop_lchown(want->uid, want->gid, is->name);
     }
-    if (want->perm != is->perm) {
+    if (!ignore_permissions && want->perm != is->perm) {
         if (!quiet)
             warn("chmod %03o %s\n", want->perm, is->name);
         fileop_chmod(want->perm, is->name);
@@ -591,7 +592,8 @@ static void usage(char *argv0) {
         "   --nice               EXPERIMENTAL nice\n"
         "   --unix-socket        EXPERIMENTAL establish data channel over ssh via AF unix sockets\n"
         "   --socket-name PATH   EXPERIMENTAL use PATH as name for AF unix sockets\n"
-        "   --noatime            don't touch atime on sender\n",
+        "   --noatime            don't touch atime on sender\n"
+        "   --ignore-permissions do not attempt to change file permissions\n",
         argv0, argv0);
     _exit(1);
 }
@@ -621,6 +623,7 @@ static struct option options[] = {
     { "unix-socket",    0, &unix_socket,        1 },
     { "socket-name",    1, NULL,                104 },
     { "noatime",        0, &noatime,            1 },
+    { "ignore-permissions",  0, &ignore_permissions,       1 },
     { NULL }
 };
 
@@ -1232,6 +1235,8 @@ static void master(char *master_path, char *target) {
         }
         if (slave_unprivileged || strcmp(slave_user, "root"))
             g_ptr_array_add(args, "--unprivileged");
+        if (ignore_permissions)
+            g_ptr_array_add(args, "--ignore-permissions");
         g_ptr_array_add(args, slave_path);
 
         g_ptr_array_add(args, NULL);