It lulled me into a false sense of comfort...
For one-click-installable software Dreamhost also offers one-click upgrades. Basically, there is this button in your control panel "upgrade to the latest version", next to each one-click-installable package that you have installed. If a button is there, it's tempting you to click it. After all, why not install the latest version? You want to be "with it", don't you? :-) And Dreamhost provides reasonable precautions against upgrades gone bad: it urges you to back up your database, and it does not destroy the old version, but moves the old directory to .old, assuring you that should you not like the new version, you can revert back to the old one simply by renaming the directory. So really, why not upgrade? Is it any wonder that my finger itched to click that button?
...and then it sprung the trap
So I clicked to upgrade my Gallery installation. And... I don't have Gallery anymore. Or rather, I have a Gallery that throws itself into an infinite loop of URL redirection whenever anybody attempts to view it. It does that because it claims it "can't" "find" the default theme plugin, called Matrix. I put the words "can't" and "find" in quotes, because it's not clear in what sense Gallery is unable to find this plugin. Matrix theme is right there where it's always been, and Gallery debug messages indicate it is indeed able to instantiate the Matrix plugin class. But after that it arrives to a conclusion that the Gallery theme is missing, inactive or incompatible.
Googling this error message and various permutations of its terms didn't yield anything useful or applicable to my situation.
Can't go back to the old version, either
What about the assurance on behalf of Dreamhost that I should be able to go back to the old version of Gallery? (They say it's as simple as renaming the .old directory back to its proper name.) Well, that didn't help -- I'm getting a different error message. Blowing away both the old and the new directories and installing from scratch is not an option either, because I have literally thousands of pictures in Gallery, painstakingly added over the course of two years. I really, really want to fix this install. Dreamhost won't be of help, because they state clearly that they don't support third-party software, and all the installations or upgrades you perform, even the one-click ones, you do at your own risk.
But I think I should still fire off a nastygram to Dreamhost. It's one thing to not support software, but it's quite another to give your users rope to hang themselves with. At the very least they could have tried out the one-click upgrade themselves, observed that it leads to a disaster, and issued a warning to users. But I've been too demoralized to fire off nastygrams.
Of course, since this is an open source program, its source code is available to me, so in theory I should be able to debug it. In theory. Given plenty of spare time. If I go that route (since I don't have many other options at this point), at least I'll be able to get a lot of blogging mileage out of it, in the spirit of Eric Raymond's CUPS rant :-) (I won't put tedious details in this blog, though.)