Add -R as a synonym to -r for cp(1)

List the available options in the usage line as well.

cp.1

@@ -3,12 +3,12 @@
 cp \- copy files and directories
 .SH SYNOPSIS
 .B cp
-.RB [ \-r ]
+.RB [ \-Rr ]
 .I file
 .RI [ name ]
 .P
 .B cp
-.RB [ \-r ]
+.RB [ \-Rr ]
 .RI [ file ...]
 .RI [ directory ]
 .SH DESCRIPTION
@@ -17,6 +17,9 @@ copies a given file, naming it the given name.  If multiple files are listed
 they will be copied into the given directory.
 .SH OPTIONS
 .TP
+.B \-R
+equivalent to -r.
+.TP
 .B \-r
 copies directories recursively.  If this flag is not specified, directories are
 not copied.

cp.c

@@ -8,7 +8,7 @@
 static void
 usage(void)
 {
-	eprintf("usage: %s source... dest\n", argv0);
+	eprintf("usage: %s [-Rr] source... dest\n", argv0);
 }
 
 int
@@ -17,6 +17,7 @@ main(int argc, char *argv[])
 	struct stat st;
 
 	ARGBEGIN {
+	case 'R':
 	case 'r':
 		cp_rflag = true;
 		break;