Question: When cloning git repositories in automated tools - web front ends, CI systems, sometimes the git clone invocation opens up a prompt asking for the username and password (for example, when cloning a non-existent Github repo or on a new node missing ssh keys).

How do I make git just fail (preferably with a sensible error message and exit code) instead of waiting for the server process to give it a username and password?

Answer: 
In git version 2.3 there's an environment variable `GIT_TERMINAL_PROMPT` which when set to `0` will disable prompting for credentials.

You can get more info about it in `man git` (after updating to git version `2.3`) or in [this blog post on github](https://github.com/blog/1957-git-2-3-has-been-released).

Examples:

* `git clone https://github.com/some/non-existing-repo` will prompt for username & password
* `GIT_TERMINAL_PROMPT=0 git clone https://github.com/some/non-existing-repo` will fail without prompting for username & password
```
GIT_TERMINAL_PROMPT=0 git clone https://github.com/some/non-existing-repo

```

Work for me on Mac.