Hide specific file from Git public Repo

There are several alternatives, including "git-crypt"

• https://buddy.works/guides/git-crypt):

• https://apiumhub.com/tech-blog-barcelona/keeping-sensitive-data-secret-git-repository/

Since you're using Heroku, this might be your best bet:

https://softwareengineering.stackexchange.com/a/182074/76526

The preferred method of keeping passwords/api keys secret on heroku is to set config values via the heroku commandline application. The following example taken from a heroku dev center article

(The below example, and my entire answer relate to rails apps)

$ cd myapp
$ heroku config:add S3_KEY=8N029N81 S3_SECRET=9s83109d3+583493190
Adding config vars and restarting myapp... done, v14
S3_KEY:     8N029N81
S3_SECRET:  9s83109d3+583493190

Then reference these config values in your code using the ENV[] variable

AWS::S3::Base.establish_connection!(
  :access_key_id     => ENV['S3_KEY'],
  :secret_access_key => ENV['S3_SECRET']
)

This way your sensitive passwords are not stored in the git repository. (Note: When running the app locally, set these values in your .bashrc file

Also, I'm not sure what type of application you are running, but in Rails, heroku does not use your database.yml file, it simply sets your database username/password according to your app settings. So you can avoid saving those credentials in git

Also, also, if you are running your own application and want it to remain private, a great alternative to github is bitbucket which offer free private repositories.

ADDENDUM:

It is working now I had to use .env instead of .bashrc and instead of ENV I had to use process.env.TOKEN, also I had to use the dotenv module at the start of the file(npmjs.com/package/dotenv) – Coder Gautam YT