#!/usr/bin/env perl

use Modern::Perl;
# The output of this should be sourced 
# Ex. git filter-branch --env-filter 'source foo.sh' HEAD

print <<'PREQUEL';
#!/bin/sh

n=$GIT_AUTHOR_NAME
m=$GIT_AUTHOR_EMAIL

case ${GIT_AUTHOR_NAME} in
PREQUEL

while( my $line = <> ){
    my @f = split /\s+=/, $line;
    if( $f[1] =~ m/\s+(.*)\s+<([^<]+)>/) {
        my ($name,$email) = ($1,$2);
        # We have to by sly about quoting
        if ( $name =~ /'/ ) {
            say sprintf '"%s") n="%s" ; m="%s" ;;', $f[0], $name, $email;
        } else {
            say sprintf '"%s") n=\'%s\' ; m="%s" ;;', $f[0], $name, $email;
        }
    } else {
        say sprintf '"%s") n="%s" ; m="%s" ;;', $f[0], $f[0], 'none@none';
    }
}

print <<'AFTERWORD';
esac

export GIT_AUTHOR_NAME="$n"
export GIT_AUTHOR_EMAIL="$m"
export GIT_COMMITTER_NAME="$n"
export GIT_COMMITTER_EMAIL="$m"

AFTERWORD