#!/usr/bin/perl
# git-history-to-subdirs subdir...
#   Go back through git's history and make it look like the present contents
#   of the given directories have always been there.

# Do this in perl because bash's variable substitution isn't up to the task.

use strict;

opendir DOT, ".";
my @files = (readdir DOT); closedir DOT;
my @dirs = ();
my %dir_lists;

foreach my $f (@files) {
    if (-d $f && ! -l $f && $f !~ /^\./) {
	push(@dirs, $f);
    }
}

foreach my $d (@dirs) {
    $dir_lists{$d} = list_directory($d);
}

my $filter_cmd = "git filter-branch --prune-empty --tree-filter '";
for my $d (keys %dir_lists) {
    $filter_cmd .= ("for f in " . join(" ", @{$dir_lists{$d}}) .
		    "; do if [ -f \$f ]; then mkdir -p $d; " .
		    "mv -f \$f $d; fi done;\n");
}
$filter_cmd .= "'\n";
system $filter_cmd;

sub list_directory {
    my ($d) = @_;
    opendir DIR, $d;
    my @list = readdir(DIR);
    closedir(DIR);
    my @filtered_list = ();
    for my $f (@list) {
	push @filtered_list, $f unless ($f =~ /^\./);
    }
    return \@filtered_list;
}