#!/usr/bin/perl
# Uses symlinks to merge the files contained in a set of subversion
# checkouts to into a single directory. Keeps track of when files are
# removed from the merged directories and removes the symlinks.
#
# Only merges files that match the specified pattern.
#
# Note that the directories given to merge should be paths that will work
# for symlink targets from the destination directory (so either full paths,
# or they should be right inside the destination directory).
#
# Note that other files in the destination directory will be left as-is.
#
# Copyright 2006 by Joey Hess, licensed under the GPL.

if (! @ARGV) {
	die "usage: svnmerge include-pattern dest dir1 [dir2 ...]\n";
}

my $pattern=shift;
my $dest=shift;

foreach my $dir (@ARGV) {
     my %known;

     # Link in each thing from the dir.
     opendir(DIR, $dir) || die "opendir: $!";
     while ($_=readdir(DIR)) {
	  next if $_ eq '.' || $_ eq '..' || $_ eq 'known' || $_ eq '.svn';
	  next unless /$pattern/;

	  $known{$_}=1;

	  if (! -l "$dest/$_" && -e "$dest/$_") {
	       print STDERR "$_ in $dir is also in $dest\n";
	  }
	  elsif (! -l "$dest/$_") {
	       system("ln", "-svf", "$dir/$_", $dest);
	  }
     }
     closedir(DIR);

     # Remove anything that was previously linked in but is not in the
     # dir anymore.
     if (-e "$dir/known") {
	  open(KNOWN, "$dir/known") || die "open $dir/known: $!";
	  while (<KNOWN>) {
	       chomp;
	       if (! $known{$_}) {
		    system("rm", "-vf", "$dest/$_");
	       }
	  }
	  close KNOWN;
     }

     # Save state for next time.
     open(KNOWN, ">$dir/known") || die "write $dir/known: $!";
     foreach my $file (sort keys %known) {
	  print KNOWN "$file\n";
     }
     close KNOWN;
}