gpg "failed to write commit object"

Question

I'm trying to enable commit signing on OS X Mojave.

git commit -S -am "Test"

The error is:

error: gpg failed to sign the data
fatal: failed to write commit object

What I tried:

• gpg works fine (see below), did not install gpg1 or gpg2
• Installed GPG KeyChain and added a new key (even added a separate sign-only subkey whithin)
• Installed pinentry
• gpg2 --clearsign works fine (generates a new .asc file for files, outputs text for plain text)

Questions I looked into and tried every option:

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

What am I doing wrong?

Answer 1

Try with echo "foobar" | gpg --clearsign. It should ask for your key's passphrase and return the signature. If instead you see the following error message:

error: gpg failed to sign the data
fatal: failed to write commit object

You might want to try running export GPG_TTY=$(tty). If after testing again you're prompted for the password and it works, run this everytime on startup, adding it to ~/.bashrc, which is actually required according to gpg-agent's documentation, as mentioned in this dev.gnupg thread and which you can verify with man gpg-agent.

I also found this gitHub gist very useful.

Answer 2

I also had this problem. I found a good solution. Just try to sign a file before you commit.

$ touch a.txt
$ gpg --sign a.txt

Then, the OS will let you input the password. If this step is OK, now you can commit by signing correctly.