Migrating from subversion to git

At work we have been migrating from subversion to git.  The projects that we still have in subversion I check out using git-svn.  This allows me to use much of the git happiness while we make the transition.  It also performs another very nice function; it allows us to migrate our repositories to git keeping our full version control history.

What follows demonstrates, from a Linux machine, to migrate a repository from http://svn.foo.com/bar to ssh://git.foo.com/repos/bar.git.  This assumes you already have git, subversion, and git subversion installed.  It also assumes that you have read access to the subversion repository, and a git repository you have direct access to.

git svn clone http://svn.foo.com/bar/trunk bar

Next we need to log into the machine hosting our git repository.  We do this over ssh.

ssh foo.com

cd ~/repos

mkdir bar.git

cd bar.git

git init --bare

Back on our machine.

cd bar

git remote add origin ssh://git.foo.com/repos/bar.git

git push origin master

You should now have a central git repository at ssh://git.foo.com/repos/bar.git  You can create your branches, and do whatever git-style version controlling that you wish.  The final step, of course, is to remove the old subversion repository so that others do not accidentally make changes that never find themselves in the real copy of the code.

One limitation is that this process does not import any branches or tags from the subversion repository.  I'm not sure if there is a clean way to do this.

Shuffling cards in PHP

The following demonstrates what I believe to be an efficient means of shuffling a deck of cards, using PHP.




$cards = array(array('suit'=>'Spade', 'rank'=>'01'), array('suit'=>'Spade', 'rank'=>'02'), array('suit'=>'Spade', 'rank'=>'03'), array('suit'=>'Spade', 'rank'=>'04'), array('suit'=>'Spade', 'rank'=>'05'), array('suit'=>'Spade', 'rank'=>'06'), array('suit'=>'Spade', 'rank'=>'07'), array('suit'=>'Spade', 'rank'=>'08'), array('suit'=>'Spade', 'rank'=>'09'), array('suit'=>'Spade', 'rank'=>'10'), array('suit'=>'Spade', 'rank'=>'11'), array('suit'=>'Spade', 'rank'=>'12'), array('suit'=>'Spade', 'rank'=>'13'), array('suit'=>'Spade', 'rank'=>'14'),
               array('suit'=>'Club', 'rank'=>'01'), array('suit'=>'Club', 'rank'=>'02'), array('suit'=>'Club', 'rank'=>'03'), array('suit'=>'Club', 'rank'=>'04'), array('suit'=>'Club', 'rank'=>'05'), array('suit'=>'Club', 'rank'=>'06'), array('suit'=>'Club', 'rank'=>'07'), array('suit'=>'Club', 'rank'=>'08'), array('suit'=>'Club', 'rank'=>'09'), array('suit'=>'Club', 'rank'=>'10'), array('suit'=>'Club', 'rank'=>'11'), array('suit'=>'Club', 'rank'=>'12'), array('suit'=>'Club', 'rank'=>'13'), array('suit'=>'Club', 'rank'=>'14'),
               array('suit'=>'Diamond', 'rank'=>'01'), array('suit'=>'Diamond', 'rank'=>'02'), array('suit'=>'Diamond', 'rank'=>'03'), array('suit'=>'Diamond', 'rank'=>'04'), array('suit'=>'Diamond', 'rank'=>'05'), array('suit'=>'Diamond', 'rank'=>'06'), array('suit'=>'Diamond', 'rank'=>'07'), array('suit'=>'Diamond', 'rank'=>'08'), array('suit'=>'Diamond', 'rank'=>'09'), array('suit'=>'Diamond', 'rank'=>'10'), array('suit'=>'Diamond', 'rank'=>'11'), array('suit'=>'Diamond', 'rank'=>'12'), array('suit'=>'Diamond', 'rank'=>'13'), array('suit'=>'Diamond', 'rank'=>'14'),
               array('suit'=>'Heart', 'rank'=>'01'), array('suit'=>'Heart', 'rank'=>'02'), array('suit'=>'Heart', 'rank'=>'03'), array('suit'=>'Heart', 'rank'=>'04'), array('suit'=>'Heart', 'rank'=>'05'), array('suit'=>'Heart', 'rank'=>'06'), array('suit'=>'Heart', 'rank'=>'07'), array('suit'=>'Heart', 'rank'=>'08'), array('suit'=>'Heart', 'rank'=>'09'), array('suit'=>'Heart', 'rank'=>'10'), array('suit'=>'Heart', 'rank'=>'11'), array('suit'=>'Heart', 'rank'=>'12'), array('suit'=>'Heart', 'rank'=>'13'), array('suit'=>'Heart', 'rank'=>'14'));
$shuffled_cards = array();
while (sizeof($cards) != 0)
{
  mt_srand((double)microtime()*1000000);
  $card = mt_rand(0, sizeof($cards) - 1);
  $shuffled_cards[] = $cards[$card];
  unset($cards[$card]);
  $cards = array_values($cards);
}
print_r($shuffled_cards);

We start by initializing our deck of fifty-two cards.  Each member of our array is an associative array holding the suit and rank of each card.  We then initialize a blank array where we will store our shuffled cards.
The while loop will execute until all of the cards have been popped out of our initial array.
At the beginning of each iteration we start a new pseudo-random seed.  Then, we get a random number between zero, and the number of cards we have left to shuffle, minus one (because arrays are zero indexed.)  Next, we append the randomly selected card to our shuffled array and remove it from our cards array.
When we remove a card from our numerically indexed array, the array becomes sparse.  So if the random number was four, then we are left with indexes one, two, three, five, six and so on.  If we hit four through another iteration, there would be no value to add to our shuffled array.
To make our array dense again, we can simply call the array_values function on our cards array and assign it back to cards.
This solution buys us a few niceties, compared to other solutions I have come across.  First, at any given time a card is only in one array (except the split moment that we are doing the move).  The second is that we don't have to worry about our random number being the same as a previously picked random number, and thus waste time picking another number until we hit a unique number.
Finally, this solution is really just an exercise in efficiently shuffling an array.  In a real application I would not use this solution at all.  PHP comes with a nice little function named, easy enough to remember, shuffle().  So let's take a look at how one should really implement the solution.


$cards = array(array('suit'=>'Spade', 'rank'=>'01'), array('suit'=>'Spade', 'rank'=>'02'), array('suit'=>'Spade', 'rank'=>'03'), array('suit'=>'Spade', 'rank'=>'04'), array('suit'=>'Spade', 'rank'=>'05'), array('suit'=>'Spade', 'rank'=>'06'), array('suit'=>'Spade', 'rank'=>'07'), array('suit'=>'Spade', 'rank'=>'08'), array('suit'=>'Spade', 'rank'=>'09'), array('suit'=>'Spade', 'rank'=>'10'), array('suit'=>'Spade', 'rank'=>'11'), array('suit'=>'Spade', 'rank'=>'12'), array('suit'=>'Spade', 'rank'=>'13'), array('suit'=>'Spade', 'rank'=>'14'),
               array('suit'=>'Club', 'rank'=>'01'), array('suit'=>'Club', 'rank'=>'02'), array('suit'=>'Club', 'rank'=>'03'), array('suit'=>'Club', 'rank'=>'04'), array('suit'=>'Club', 'rank'=>'05'), array('suit'=>'Club', 'rank'=>'06'), array('suit'=>'Club', 'rank'=>'07'), array('suit'=>'Club', 'rank'=>'08'), array('suit'=>'Club', 'rank'=>'09'), array('suit'=>'Club', 'rank'=>'10'), array('suit'=>'Club', 'rank'=>'11'), array('suit'=>'Club', 'rank'=>'12'), array('suit'=>'Club', 'rank'=>'13'), array('suit'=>'Club', 'rank'=>'14'),
               array('suit'=>'Diamond', 'rank'=>'01'), array('suit'=>'Diamond', 'rank'=>'02'), array('suit'=>'Diamond', 'rank'=>'03'), array('suit'=>'Diamond', 'rank'=>'04'), array('suit'=>'Diamond', 'rank'=>'05'), array('suit'=>'Diamond', 'rank'=>'06'), array('suit'=>'Diamond', 'rank'=>'07'), array('suit'=>'Diamond', 'rank'=>'08'), array('suit'=>'Diamond', 'rank'=>'09'), array('suit'=>'Diamond', 'rank'=>'10'), array('suit'=>'Diamond', 'rank'=>'11'), array('suit'=>'Diamond', 'rank'=>'12'), array('suit'=>'Diamond', 'rank'=>'13'), array('suit'=>'Diamond', 'rank'=>'14'),
               array('suit'=>'Heart', 'rank'=>'01'), array('suit'=>'Heart', 'rank'=>'02'), array('suit'=>'Heart', 'rank'=>'03'), array('suit'=>'Heart', 'rank'=>'04'), array('suit'=>'Heart', 'rank'=>'05'), array('suit'=>'Heart', 'rank'=>'06'), array('suit'=>'Heart', 'rank'=>'07'), array('suit'=>'Heart', 'rank'=>'08'), array('suit'=>'Heart', 'rank'=>'09'), array('suit'=>'Heart', 'rank'=>'10'), array('suit'=>'Heart', 'rank'=>'11'), array('suit'=>'Heart', 'rank'=>'12'), array('suit'=>'Heart', 'rank'=>'13'), array('suit'=>'Heart', 'rank'=>'14'));
shuffle($cards);
print_r($cards);

Sucrose Progression

This was made using the Cat and Girl Maker  The artwork is all Dorothy Gambrell, the dialog is mine.  The style is meant to closely resemble Dorothy's style for her Cat and Girl comics.

Updating JOSM in Ubuntu

If you are a contributor to Open Street Map, and you run Ubuntu, then you probably use JOSM from time-to-time.  It has a lot of great tools that are not available in the online editor.  My favorite is the Orthogonalize Shape tool.
Anyhow, I got tired of being told to update each time I started the application.  Plus, I like being up to date.  Since Ubuntu only gets an updated version of JOSM with each new release of Ubuntu, I decided to find out how to cleanly update JOSM in a way that integrates well with the currently installed JOSM.  Here's what I did.

1. Go to http://josm.openstreetmap.de/
2. Under the Download section, click on the "tested JOSM" link and save it.
3. Under a terminal run the following.
   sudo cp ~/Downloads/josm-tested.jar /usr/share/josm/
   cd /usr/share/josm/
   sudo ln -f -s josm-tested.jar josm.jar
   
Change ~/Downloads/josm-test.jar to the location in which you saved the josm-tested.jar file.

Now when you run JOSM the way you always have, it will load the latest stable version of JOSM.

When you first start JOSM you should go ahead and update your plugins.

This was testing in Ubuntu Lucid 10.04, but should work with any version of Ubuntu, and with any version of JOSM.  If it doesn't for any reason, respond in the comments below.