Merge branch 'ps/maintenance-geometric-default' into next
"git maintenance" starts using the "geometric" strategy by default.
* ps/maintenance-geometric-default:
builtin/maintenance: use "geometric" strategy by default
t7900: prepare for switch of the default strategy
t6500: explicitly use "gc" strategy
t5510: explicitly use "gc" strategy
t5400: explicitly use "gc" strategy
t34xx: don't expire reflogs where it matters
t: disable maintenance where we verify object database structure
t: fix races caused by background maintenance