Git bundle create produces inconsistent bundle

[Andre Loconte <andre.loconte@protonmail.com>]

Hello,

I am running into an issue where "git bundle create" doesn't always produce the same bundle, provided the exact same arguments and the exact same repo.

Where it gets tricky is that:

- I cannot reproduce the issue with random repos from Github (tried with ~10 repos and 30 bundles per repo);
- I cannot reproduce the issue with the same OS and git version on different hardware ;
- I can reproduce the issue on colleagues' workstation (environment is identical down to the hardware, see below).

Environment:

- GNU/Linux 5.3.0-24-generic Ubuntu 19.10 x86_64 ;
- git version 2.20.1 ;
- Intel Xeon Silver 4114 CPU @ 2.20GHz × 20 ;
- 4 × Hynix HMA81GR7CJR8N-VK 8GB DDR4-2666 ECC.

I have put together a bash PoC [1]. And there are some example output in the comments (consistent [2], inconsistent [3]).

[1] https://gist.github.com/alct/05cc9a2b4657d51669c96cb22cd5c4a6
[2] https://gist.github.com/alct/05cc9a2b4657d51669c96cb22cd5c4a6#gistcomment-3130206
[3] https://gist.github.com/alct/05cc9a2b4657d51669c96cb22cd5c4a6#gistcomment-3130213

I cannot share the affected repos but I can run any diagnostic tool against them.

Would you have any clue on what could produce such behavior?

Best,

A.L.