Massive libgit2 performance regression observed in Kubuntu 25.04 and Windows 11

Summary

In the version of libgit2 bundled with kubuntu 25.04 (1.9.0+ds-1ubuntu1) there is an enormous performance regression compared with the version bundled with 24.10. I built the library myself to narrow the issue down. I conducted a binary search of git commits and narrowed it down to fb1797de6307d8f705f9079e759860234a10de07, which is the first commit that shows the problem: the parent 93c94446cd69bec6d4a2e61e9384ebfa159d1e19 is fine. (These are between the v1.8.0 and v1.8.1 tags.)

Reproduction

Using kubuntu 25.04 (I have tested with a clean installation):

• Clone the libgit2 repository
• Check out revision 93c94446cd69bec6d4a2e61e9384ebfa159d1e19 and build
• Run ctest -V. Time is normal: my output is here ctest-93c94.txt and the overall time is 194.92 s.
• Check out revision fb1797de6307d8f705f9079e759860234a10de07 and build
• Run ctest -V. Time is extremely slow: my output is here ctest-fb1797.txt and the overall time is 996.67 s.

The biggest slowdowns occur in the online::badssl test (test 3 goes from 34.08 s to 434.25 s most of which time was stuck on the badssl test) and test 10 auth_clone which goes from 2.58 s to 402.93 s.

This is absolutely crippling performance in applications that use libgit2, for example Siril uses it to clone or fetch a repository at startup and it has gone from being unnoticeable (< 1 s) to taking approx. 6 minutes.

I'll be happy to provide any further help in terms of testing things, just let me know.

Compare revisions 93c94446cd69bec6d4a2e61e9384ebfa159d1e19 and fb1797de6307d8f705f9079e759860234a10de07, then run ctest -V on each build. Focus first on online::badssl test 3 and auth_clone test 10, using the attached timing logs to identify the regression. Done means the affected tests no longer show the reported slowdown on Kubuntu 25.04 and Windows 11.