Had a report of close throwing ErrorBusy on CIFS.
Retrying up to 16 seconds is a balance between hopefully waiting long
enough for the problem to clear up and waiting so long that git-annex seems
to hang.
The new dependency is free; persistent depends on unliftio-core.
I just had a test that crashed at cleanup on linux with:
.t/gpgtest/12/S.gpg-agent.browser: removeDirectoryRecursive:removeContentsRecursive:removePathRecursive:removeContentsRecursive:removePathRecursive:removeContentsRecursive:removePathRecursive:getSymbolicLinkStatus: does not exist (No such file or directory)
sleeping 10 seconds and will retry directory cleanup
git-annex: .t/gpgtest/14/S.gpg-agent.browser: removeDirectoryRecursive:removeContentsRecursive:removePathRecursive:removeContentsRecursive:removePathRecursive:removeContentsRecursive:removePathRecursive:getSymbolicLinkStatus: does not exist (No such file or directory)
removePathForcibly is supposed to be more robust to things in the directory vanishing while it's running, etc.
Will probably avoid such crashes.
It was added to directory-1.2.7, which comes with ghc since 8.0.2.
Since base >= 4.11.1.0 means ghc 8.4.4, I expect all builds will have it,
but I ifdefed it to be sure.
This avoids some extra work, but I don't think it was possible for two ssh
endpoint discoveries run concurrently to both prompt for the ssh password;
Annex.Ssh itself deals with concurrency.
This is mostly groundwork for http password prompting.
