Add base git configuration via file

[drewbo]

The incident resolution deployed in #397 runs git config ... via subprocess but this option (and other potential configuration settings) can be set via file in the build image rather than at container run time

Acceptance Criteria

• Review which git configuration options we should set as default for the build
• Add a configuration file to the built image
• Confirm expected behavior on staging environment
• Deployed to production build container