[git] handle attempting to sign-off without configs

[vince-fugnitto]

What it does

Fixes #4908

Handle the toolbar action to add a sign-off when the
user does not have their user.name and user.email configured.

How to test

1. ensure that the git config is not set (ex: open ~/.gitconfig and comment out user.name and user.email entries
2. attempt to create a commit in the application, and click the sign-off toolbar button
3. a warning should be displayed that no config is set
4. un-comment out the entries in the gitconfig
5. retry step 2, the sign-off should be added in the commit message

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

Signed-off-by: vince-fugnitto vincent.fugnitto@ericsson.com

[vince-fugnitto]

I was debating over whether to use a warning directly bellow the input or through the message-service. I ultimately decided on bellow the input since the sign-off directly affects the commit message. If others have any other opinions please let me know.

[kittaakos]

I have verified it in GItpod with the following commands:

git config --global --unset user.name
git config --global set user.name "Foo Bar"

It worked as described. 👍