/etc/gitconfig shipped `helper = git-credential-hive-forge`. git prepends
`git-credential-` to any helper value that is not an absolute path, so
that resolves to `git-credential-git-credential-hive-forge`, which does
not exist -- no helper runs at all. The sibling github.nix has always used
the short form.
Measured rather than read off the docs, with the arms isolated from the
personal ~/.gitconfig:
helper = git-credential-hive-forge -> 0 credentials, and git prints
"'credential-git-credential-hive-forge' is not a git command"
helper = hive-forge -> 1 credential, clean stderr
The reason this survived: every long-lived agent has a personal
~/.gitconfig naming the helper by ABSOLUTE path, which git accepts, so
pushes keep working and the stderr line reads as noise. The system config
is masked exactly where someone would notice it and bites a fresh agent
that has no such file.
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