Git hash prefix or cellphone number?

Today, I was playing around with a new feature in Gaia Sky, and I created a new release from master. Immediately, I noticed something unusual in the generated package name:

packages-3.8.0.066962508

The 3.8.0 part is the release version, while the last 9 characters are the abbreviated Git commit hash. Usually, that last part looks something like:

packages-3.8.0.a31f7c92e

This time, however, every single one of the hash characters is a number, 066962508. My first stupid reaction was thinking that something had gone wrong. However, git log confirmed the hash was fine.

➜ git log

commit 066962508de536403a185471344ba83801d45a88 (HEAD -> master, origin/master, origin/HEAD, gitlab/master, gitlab/HEAD, github/master, github/HEAD)
Author: langurmonkey <tsagrista_AT_ari.uni-heidelberg.de>
Date:   Tue Sep 29 10:10:15 2026 +0200

    feat: Handle gaiasky:// URLs forwarded from second instances and macOS open events. Part of #935.
    
    - Scope dataset URL dedup to the startup path only, so re-sent URLs are always processed by the running instance.
    - Register install4j StartupNotification listener for macOS open-URL events, with pending-URL queue for pre-UI arrival.
    - Add --enable-native-access=ALL-UNNAMED to launcher VM parameters - Add compileOnly install4j-runtime dependency.

Obviously, I asked myself, “how likely is that”? So I did some digging.

Git commit hashes are hexadecimal. That means each character can be one of 16 possible values:

0 1 2 3 4 5 6 7 8 9 a b c d e f

So there’s nothing special about a hash starting with 066962508. It’s just a hexadecimal string that happens to contain no a–f characters in its first nine positions.

But how unlikely is that?

There are 10 numerical characters out of 16 possible hexadecimal characters, so the probability of a single character being a number is:

$$ \frac{10}{16} = 0.625 $$

For nine consecutive characters to all be numbers:

$$ \left(\frac{10}{16}\right)^9 \approx 0.0145 $$

That’s about 1.45%, or roughly 1 in 69.

So it’s not particularly likely, but it’s certainly not extraordinary either. Given enough commits, you’re bound to run into one eventually. It looks even stranger because of the leading zero, and a quick glance at the number may even make someone mistake it for a Spanish cellphone number.

I wondered whether this was the first time this had happened in the Gaia Sky repository, so I ran:

➜ git log --all --format='%H'
    | grep -E '^[0-9]{9}'
    | wc -l

123

Nope. It has happened over a hundred times, and I had simply never noticed it before. I’m pretty sure this is the first time I package a build from one of those commits though.