Well, OK, it's a crappy default recolor that changes a few things. There's been thousands of them over Minecraft's lifetime. There's no way to tell which one it is as they're all pretty much the same.
If you want this pack, you can probably just make it yourself. It's about as basic as they come and learning how to do it might just get you interested in going further. Hopefully to make some original art rather than just editing Mojang's.
Just don't post recolors here, OK? Default edits are against the Forum Rules.
Dude this is not a recolor. Look at the swoords. Ive known this texture pack before and it was well known in the MCSG community back in 2013. Look trough the vid before saying that,
The swords are default edits too. So much so that I didn't even notice on my first watching. Just slightly more impressive ones.
Though really it's just enlarge > select color > new layer > inner shadow so far as I can tell. Hard to get a good bead on it given that the entire video is nothing but a blur of action. The point is that they're still derivative if not precisely a "recolor".
And yes, I was being a bit tongue-in-cheek with that proclamation of it just being default. Sorry about that.
The point does still stand, though. It's mechanical edits and Photoshop tricks. Nothing more, and nothing particularly original. And that makes it hard to track down to any source besides Mojang. But inversely, it makes it quite easy to replicate if you desire to do so.
Why not ask on the MCSG subreddit since you say it was popular there? No idea if that'll help, but given that this community doesn't allow default edits, and so is less familiar with specific ones, you might have a better time of it elsewhere.