Add gpg setting support

[LinuxSuRen]

brew install gnupg gnupg2 pinentry-mac
git config --global user.signingkey <YOUR_SIGNING_KEY>
git config --global commit.gpgsign true
git config --global gpg.program gpg

Put the following in gpg.conf file (edit file with nano ~/.gnupg/gpg.conf command):

no-tty
Put the following in gpg-agent.conf file (edit file with nano ~/.gnupg/gpg-agent.conf command):

pinentry-program /usr/local/bin/pinentry-mac

Update:

You might need to execute killall gpg-agent command after editing the configurations file, gpg.conf, according to the comments. As the self-explanatory command says, this command will terminate the GPG (Gnu Privacy Guard) agent.

See also https://stackoverflow.com/questions/39494631/gpg-failed-to-sign-the-data-fatal-failed-to-write-commit-object-git-2-10-0