title: how to get git and gpg working together again
body: <p>I'm trying to revive a project I've been ignoring for about a decade, and find that my tools are not working.  I'm on Xubuntu 20.04, all software up-to-date.  When I try to make a new git commit, it fails with a complaint about gpg.  In fact, if I start a new git repository, the first commit fails, so it's not a problem in the data I'm committing, but my configuration is messed up.</p>
  <p>The message is always the same:</p>
  <pre><code>me@here$ git commit -a
  error: gpg failed to sign the data
  fatal: failed to write commit object
  me@here$
  </code></pre>
  <p>When I ask it to, gpg lists a single RSA key, attributed to one of my emails, dated last year.  I created it when I learned GitHub was phasing out passwords, but I'm not sure I
  ever used it.</p>
  <p>Other symptoms</p>
  <ul>
  <li>when I attempt gpg --sign (with something in stdin) I get a popup dialog asking me for a passphrase.  I have no recollection of that, and I did not make any note of such a thing in the place I would normally do that.</li>
  </ul>
  <p>So the questions are:</p>
  <ul>
  <li>what else can I do to figure out exactly what is broken</li>
  <li>how can I fix it</li>
  </ul>