gpg failed to sign the data fatal: failed to write commit object [Git 2.10.0]

Question

I followed few articles over the pretty attributes on Git 2.10 release note. Going through which upgraded the git to 2.10.0 and made changes to global .gitconfig

Answer 1

This started happening all of a sudden for me on Ubuntu, not sure if some recent update did it, but none of the existing issues were applicable for me (I had GPG_TTY set, tried killing the agent etc.). The standalone gpg command was failing with this error:

$ echo "test" | gpg --clearsign
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

test
gpg: signing failed: Operation cancelled
gpg: [stdin]: clear-sign failed: Operation cancelled

I tried running gpg with --debug-all option and noticed the below output:

gpg: DBG: chan_3 <- INQUIRE PINENTRY_LAUNCHED 27472 gnome3 1.1.0 /dev/pts/6 screen-256color -
gpg: DBG: chan_3 -> END
gpg: DBG: chan_3 <- ERR 83886179 Operation cancelled 
gpg: signing failed: Operation cancelled

The above indicates that there is some issue with the pinentry program. Gpg normally runs pinentry-curses for me, so I changed it to pinentry-tty (I had to aptitude install it first) and the error went away (though I no longer get the fullscreen password entry, but I don't like that anyway). To make this change, I had to add the line pinentry-program /usr/bin/pinentry-tty to ~/.gnupg/gpg-agent.conf and kill the agent with gpgconf --kill gpg-agent (it gets restarted the next time).