Make GPG Pass store path configurable by git config

[ipitsyn]

I found this change beneficial when using conditional git configuration includes for multiple git identities and pass password stores. It lets me transparently select appropriate password store without need to set its path explicitly by environment variable.
For example:

~/.config/git/config:

[user]
	name = John Doe
	email = [email protected]

[credential]
	credentialStore = gpg
	helper = /usr/local/bin/git-credential-manager
	gpgPassStorePath = /home/jdoe/.password-store

[includeIf "gitdir:~/Work/"]
	path = config.work

~/.config/git/config.work:

[user]
	name = John Doe (Umbrella Corp.)
	email = [email protected]

[credential]
	gpgPassStorePath = /home/jdoe/.password-store.umbrella

[mjcheetham]

This looks great thanks! Please can you undo the change to the VERSION file, and also can I ask that you add a new section to the docs/config.md file for the new config setting entry?

[mjcheetham]

Please revert this change to the VERSION file.. this is only updated by maintainers just before a release.

[ipitsyn]

Thanks @mjcheetham, requested has been done.

[mjcheetham]

Merging as broken links are not related to this PR.

Thanks for this contribution!