gistfile1.txt

#!/usr/bin/env perl

use strict;
use warnings;

use Cwd qw( cwd );
use Git::Wrapper;

my ( $old, $new, $main, $remote ) = @ARGV;

die "Need an old and new name to rename a branch"
    unless $old && $new;

my $git = Git::Wrapper->new( cwd() );

my %branches = map { s/^\*?\s+//; $_ => 1 } $git->branch();

$main   //= 'master';
$remote //= 'origin';

$git->checkout($main);
$git->push( $remote, $old );
$git->branch( '-t', $old, $remote . '/' . $old )
    unless $branches{$old};
$git->branch( '-m', $old, $new );
$git->push( $remote, $new );
$git->push( $remote, ':' . $old );
$git->branch( '-D', $new )
    unless $branches{$old};
$git->remote( 'prune', 'origin' );

print "\n  Renamed $old to $new and pushed to origin\n\n";