annex-ssh-options dropped since 8.20200330

When debugging some ssh-related datalad tests that hang with newer git-annex versions, I noticed that there was a regression in the treatment of annex-ssh-options in c8fec6ab0 (Fix a minor bug that caused options provided with -c to be passed multiple times to git, 2020-03-16).

Here's a demo script. Pointing SSHURL to any ssh-accessible annex repo should do. In the case below, the target is an annex repo with one commit and no files in the working tree.

SSHURL="smaug:/home/kyle/scratch/repo"

cd "$(mktemp -d ${TMPDIR:-/tmp}/gx-ssh-opts-XXXXXXX)"
git clone "$SSHURL" ./ >/dev/null 2>&1
git annex init \
    -c annex.sshcaching=false \
    -c remote.origin.annex-ssh-options="-o ControlMaster=auto -S CACHE" \
    --debug 2>&1 | grep 'read: ssh'

With the parent of the above commit checked out (b166223d4), the script outputs

[2020-06-30 11:09:43.853918422] read: ssh ["smaug","-o","ControlMaster=auto","-S","CACHE","-n","-T","git-annex-shell 'configlist' '/home/kyle/scratch/repo' '--debug'"]

With c8fec6ab0 checked out, it outputs

[2020-06-30 11:11:03.833678263] read: ssh ["smaug","-S",".git/annex/ssh/smaug","-o","ControlMaster=auto","-o","ControlPersist=yes","-n","-T","git-annex-shell 'configlist' '/home/kyle/scratch/repo' '--debug'"]
[2020-06-30 11:11:04.448046366] read: ssh ["-O","stop","-S","smaug","-o","ControlMaster=auto","-o","ControlPersist=yes","localhost"]

It looks like the options specified via remote.origin.annex-ssh-options are dropped, and git-annex switches to using its built-in ssh caching.

A recent commit on master (95b8b4a5a) shows the same behavior.

I've tried to work through the config-related handling and understand why the condition from c8fec6ab0 results in the ssh options being dropped, but I haven't made any progress yet.