Re: [Feature request] Add config option to gpgsign IFF key is present

From: brian m. carlson <sandals@crustytoothpaste.net>
Date: Mar 11, 2018, 17:21 UTC
Message-ID: <20180311172142.GA249931@genre.crustytoothpaste.net>
In-Reply-To: <CY1PR02MB13991271133B3A6BD334328DF4DD0@CY1PR02MB1399.namprd02.prod.outlook.com>

On Sat, Mar 10, 2018 at 03:28:43PM +0000, NELSON, JOSHUA Y wrote:

Show 9 quoted lines

> Currently, `commit.gpgsign` allows you to give either 'true' or 'false' as a value. If the key is not present, commits will fail:
> 
> ```sh
> $ git commit -m "example"
> error: gpg failed to sign the data
> fatal: failed to write commit object
> ```
> 
> I like to reuse my config file across several machines, some of which do not have my GPG key. Would it be possible to add an option to sign the commit only if the private key for `user.signingkey` is present? It could be named something like `commit.gpgsign=default-yes`.

Unfortunately, this isn't always possible. You can forward the Unix socket for the agent over an SSH connection, at which point the remote machine has the ability to sign, but the gpg client doesn't list those as existing secret keys in its output (because technically, those keys don't exist on the remote system). I use this technique at work, for example, to sign things on my development VM.

It might be possible to make the failure of the signing operation not be fatal in this case, although that could cause people to fail to sign due to transient failures even when the key is present on the system.

I usually handle this by storing my main configuration in ~/.gitconfig and on machines where I have a key, additionally having a ~/.config/git/config file that contains the commit.gpgsign entry.

-- 
brian m. carlson / brian with sandals: Houston, Texas, US
https://www.crustytoothpaste.net/~bmc | My opinion only
OpenPGP: https://keybase.io/bk2204