Currently the answer is no Yes, but not using an environment variable.
My use case is simple; I'd like to avoid accidentally checking in changes that I've made to a specific file so I can run my code locally.
Let's say I add my super secret password to the src/assets/secrets.xml
file so that I can run my code locally, but I never want my password to leak to github so it can be found with tools like this.
Originally I thought having the ability to export GITIGNORE=path/to/that/file
would be helpful in this circumstance.
But since that's not an option, here's how to accomplish the same goal.
git update-index --assume-unchanged src/assets/secrets.xml
To undo this effect:
git update-index --no-assume-unchanged src/assets/secrets.xml
After re-reading the OP's question a couple of times, I'm not sure if this will do what he's asking.