So he is jokingly showing you a way to create a Github poison pill. The joke is that if you include this 'illegal' hash you subject the repo to being DMCA'd out (not really, but it's sort of an 'imagine if'). Which means his repo is now unpublishable on Github (for long anyway).
It's kind of hacker humour in the sort of vein that you'd expect from an old-schooler like him. You sort of have to get the joke to get the joke.
Since as far as I can tell, Github isn't actually banning specific hashes (because they care about the content, not the hashes), and there's no sign that they're going to do so in the future, I can't say I understand the humor...
So, the hacker humor point is that you have a "poison" repo which, if you push it to GitHub, might get your account deleted in the future. You have no guarantee that it won't, for sure.
EDIT: I read the article again and couldn't find any of that, so I must have read that in a comment here on HN instead.
A git repo is fundamentally composed of 3 object types:
* Blob (effectively a file)
* Tree (which refers to collection of Blobs and Trees, effectively a dir)
* Commit (comment/ author info and various other metadata, a Tree, and a previous Commit)
This is what the git tools are used to dealing with. However git submodules changed things. With submodules, a Tree object can also contain a commit object! Together with the .gitmodules metadata file, this allows you to include another git repo inside your repo.
Joey leveraged that ability to add the youtube-dl latest master commit into his repo as a submodule, but deleted the .gitmodules file so that git wouldn't be verbose about it.
And that's how you sneak a commit into a repo.
This additionally leverages GitHub's data model (which is really the git data model), where they just have this huge DB of all the objects of all the repos on GitHub. So effectively by including this commit in a repo on GH, you're making it refer to the the entire (buried) youtube-dl repo, but you need to be sneaky to be able to see it.
Beyond that, it seems like a very community-hostile move to intentionally embed commit hashes that would even potentially cause a user to get banned from another platform if they push a copy of the code there. This doesn’t stick it to GitHub, it sticks it to the users of your repo.
Honestly if a user did get banned for sharing that poisoned repo, I would still put 95% responsibility for that on GitHub. But it's not happening yet as far as I know.
If they figure it out, then ROT14 it.
If they figure that out, encrypt it and post the key somewhere that blocks the offices of Github.
If they figure that out, we'll still find a way to build a better mouse.
Far better would be to spend your efforts finding which RIAA members pressed the RIAA to make this takedown. Follow the money, cui bono, etc.
Rosa Parks was asked to leave, but she didn't leave.
Github is extremely close to having a monopoly, leaving is the only way to prevent it from happening. If it becomes one, it has no incentives to listen to a few protests.
The problem lies with whichever member organizations inside the RIAA (or nonmember orgs friendly with the RIAA) convinced them to file the takedown. Most of us aren't positioned to find that out, but that's where the most can be gained. Maybe the EFF or similar orgs can help. Then we'll know what the true motives were, and how to address them.
Right now they're issuing what, 1 takedown notice to GitHub? When we make that 100,000 takedown notices, some in ROT13, some in ROT24 on an Israeli server, some in RSA encryption on a Chinese server with keys published on Russian servers, maybe they'll just be too overwhelmed with paperwork at that point.
Edit: On second thought, I just visited riaa.com . How about we lobby jQuery, WordPress and bootstrap to add a specific exclusion to their licensing? Now, this wouldn't affect the RIAA immediately, only the next time they update.
Git has a mechanism called "submodules" which allows one repo to reference another repo. It doesn't actually include any of the content from the second repo: all that's included is the URL (in the file .gitmodules) and a commit hash (in Git's view of the directory structure).
When you clone a Git repository with submodules and you pass an option to git clone, or if you run a git submodule command later, Git will make a nested clone at whatever subdirectory path contains the submodule, and check out that commit. If you make commits in the submodule (and, hopefully, remember to push them), the outer repo will appear to be modified, and you can git add the changes, which will record the new commit hash, but only the hash.
The purpose is to deal with vendoring or sometimes making changes to large repositories owned by someone else without copying the whole source code into your own repository. (It's also occasionally used as a mechanism to split up very large repositories that are owned by the same group/organization, e.g., if you have a test suite or large data files or something, or a shared library used by multiple projects, you might find it helpful to use submodules.) https://github.com/ceph/ceph is an example repo that uses them - "ceph-object-corpus" and "ceph-erasure-code-corpus" at the top level are submodules, and if you click on the .gitmodules file, you'll find that there are other submodules inside src/, too. This is also an example of how GitHub handles submodules also hosted on GitHub - it will link you to the submodule at that commit.
So, GitHub does at least some parsing of submodules. The author is claiming that if you include a banned commit hash as a submodule in the history of your own project, and then promptly delete it, it won't noticeably increase the size of your Git repo, nor will you actually include any of the banned content yourself, but GitHub will potentially prevent that history from being pushed. As a result, you have a Git repo that GitHub would not accept.
Since the author both does not use GitHub and wants to encourage others to do the same, this would be a fairly effective way of forcing that.
(The article doesn't show GitHub actually refusing to accept the history containing this submodule, though - it only shows the submodule having been created, locally. Although maybe the author's argument is simply that pushing it violates the Terms of Service even if it's not blocked by automated means.)