I see that enableremote changes the source remote to log the presence of a new annex (the annex where enableremote was called). I have tested with a gcrypt remote and I see that a new commit appears in the git-annex branch of the source remote after enableremote was called. Since I have cloned the annex just for testing and will delete it afterwards, I would like to leave the original remote untouched.
Is there a way to enable the remote read-only?

git-annex auto-init the local repository whenever it sees it's not enabled and there is a git-annex branch (or origin/git-annex etc). This is what adds the uuid of the local repository to remote.log. So, it's not specific to
enableremote; many git-annex commands will do the same thing. And git-annex needs to allocate a uuid for the local repo in order to work.One way to deal with it is to use
git annex reinitso it uses some already existing uuid. Although then getting files etc will update the records using that uuid. Might be ok if you have one uuid, perhaps one you've marked dead, that you use for this purpose and don't care what's recorded for that uuid.Or, it might be better to let git-annex auto-init a new uuid, and just configure this test repo to not push changes out to elsewhere. For example,
git config remote.origin.annex-readonly truewill makegit annex syncavoid pushing back to the origin remote.