Jenkins, git and ssh in a corporate environment

I reinstalled a later version of jenkins in order to dodge a CVE and found that git clone would no longer work. The terminal that started jenkins was getting messages prompting for the git ssh passphrase. The jenkins job just sat there on the git clone command without making any progress. I puzzled over this for ages. The previous version of jenkins had been working fine. I restarted the ssh agent but it had no effect. I googled to find out how to change my ssh credentials such that I had no passphrase (ill-advised though that may sound) and found articles claiming it was impossible. Well, it turns out it is possible. I did it and the jenkins problems went away. I don't like having an empty passphrase, it seems like bad practise, but hey, ho, needs must. So here's how I reset the passphrase to be empty: the ssh-keygen -p command prompts for the current passphrase. Enter it, then when ity asks for the new one (and confirmation) just hit return. Job done.