Reimplementation of PR#140, all kudos go to @lopsided98

As I couldn't exactly see what the merge errors were Github was
complaining about. I decided to re-implement the changes.

NOTE: I am still testing them!

README.md

@@ -202,6 +202,10 @@ As of 1.4.18, syncoid also automatically supports and enables resume of interrup
 
 	This prints a list of snapshots during the run.
 
++ --no-privilege-elevation
+
+  Bypass the root check and assume syncoid has the necessary permissions (for use with ZFS permission delegation).
+
 + --sshport
 
 	Allow sync to/from boxes running SSH on non-standard ports.

syncoid

@@ -19,7 +19,7 @@ use Sys::Hostname;
 my %args = ('sshkey' => '', 'sshport' => '', 'sshcipher' => '', 'sshoption' => [], 'target-bwlimit' => '', 'source-bwlimit' => '');
 GetOptions(\%args, "no-command-checks", "monitor-version", "compress=s", "dumpsnaps", "recursive|r",
                    "source-bwlimit=s", "target-bwlimit=s", "sshkey=s", "sshport=i", "sshcipher|c=s", "sshoption|o=s@",
-                   "debug", "quiet", "no-stream", "no-sync-snap", "no-resume", "exclude=s@", "skip-parent", "identifier=s") or pod2usage(2);
+                   "debug", "quiet", "no-privilege-elevation", "no-stream", "no-sync-snap", "no-resume", "exclude=s@", "skip-parent", "identifier=s") or pod2usage(2);
 
 my %compressargs = %{compressargset($args{'compress'} || 'default')}; # Can't be done with GetOptions arg, as default still needs to be set
 
@@ -1031,7 +1031,7 @@ sub getssh {
 		$rhost =~ s/:\Q$fs\E$//;
 		my $remoteuser = $rhost;
 		 $remoteuser =~ s/\@.*$//;
-		if ($remoteuser eq 'root') { $isroot = 1; } else { $isroot = 0; }
+		if ($remoteuser eq 'root' || $args{'no-privilege-elevation'}) { $isroot = 1; } else { $isroot = 0; }
 		# now we need to establish a persistent master SSH connection
 		$socket = "/tmp/syncoid-$remoteuser-$rhost-" . time();
 		open FH, "$sshcmd -M -S $socket -o ControlPersist=1m $args{'sshport'} $rhost exit |";
@@ -1249,4 +1249,5 @@ Options:
   --quiet               Suppresses non-error output
   --dumpsnaps           Dumps a list of snapshots during the run
   --no-command-checks   Do not check command existence before attempting transfer. Not recommended
+  --no-privilege-elevation  Bypass the root check, for use with ZFS permission delegation
   --no-resume           Don't use the ZFS resume feature if available