git error: RPC failed; HTTP 400 curl 22 The requested URL returned error: 400

Some job logs report RPC failed.

2024-05-16 06:53.54: Waiting for worker…
2024-05-16 06:53.54: Got resource from pool OCluster
Building on summer
error: RPC failed; HTTP 400 curl 22 The requested URL returned error: 400
fatal: unable to write request to remote: Broken pipe
git-fetch failed with exit-code 128
2024-05-16 06:53.58: Job failed: Failed: Build failed

On the FreeBSD system, in /var/log/messages, the failure relates to git fetch:

May 16 06:58:13 summer root[92057]: 2024-05-16 06:58.13         worker [INFO] Exec(git-fetch): "git" "-C"
May 16 06:58:13 summer root[92057]:                                           "/obuilder/state/git/opam-repository.git-b322f7b18d276db68487afc3dfc5a5befdd45818"
May 16 06:58:13 summer root[92057]:                                           "fetch" "-q" "--update-head-ok"
May 16 06:58:13 summer root[92057]:                                           "--recurse-submodules=no" "origin"
May 16 06:58:14 summer root[92057]: 2024-05-16 06:58.14         worker [INFO] Job failed: git-fetch failed with exit-code 128

Running git -C /obuilder/state/git/opam-repository.git-b322f7b18d276db68487afc3dfc5a5befdd45818 fetch -q --update-head-ok --recurse-submodules=no origin on the command line gives the same error.

Running git config --global http.postBuffer 524288000 as suggested on Stack overflow and then copying the .gitconfig to / seems to work around this issue. Copying to / is required as git is running as root without a $HOME environment variable.