title: Git stopped asking for password when signing commit
body: <p>I set up git to allow GPG signing of commits. It was working fine but recently I've noticed that sometimes I am not prompted for a passphrase and I get the message <code>You need a passphrase to unlock the secret key for user:</code> when committing with the <code>-S</code> flag, although the commit still goes through. Other times I am prompted for the passphrase and everything works as usual.</p>
  
  <p>The strange thing is that when I check <code>git log --show-signature</code> it shows that the commits that did not prompt for a passphrase are listed as having a good signature just like the others.</p>
  
  <p>I'm running Ubuntu 14.04, git 1.9.1, and GnuPG 1.4.16.</p>
  
  <p>I was thinking that it had something to do with how Ubuntu doesn't make enter your sudo passphrase if you have entered it recently. But I don't see how this would affect git.</p>