Make WSL bash execute .bashrc (to support ssh-agent)

[rennex]

I had to make this change to enable using ssh-agent which I have configured in .bashrc (according to GitHub's instructions, which I guess describes the common technique). This enables pushing to and pulling from remote repos using ssh keys, without leaving a passwordless ssh key on your disk.

A simple wsl some commands in cmd.exe doesn't seem to make bash run .profile, .bash_profile, nor .bashrc, so running wsl bash -ic 'some commands' looks like the only solution.

These changes seemed to work for me, but feel free to re-think it, make it configurable, or something. But I think something like this needs to be implemented.

[hangxingliu]

I think it will be better if implemented like following snippet:

fn use_interactive_shell() -> bool {
    // check for explicit environment variable setting
    if let Ok(interactive_flag) = env::var("WSLGIT_USE_INTERACTIVE_SHELL") {
        if interactive_flag == "false" || interactive_flag == "0" {
            return false;
        }
    }
    // check for advanced usage indicated by BASH_ENV and WSLENV=BASH_ENV
    else if env::var("BASH_ENV").is_ok() {
        if let Ok(wslenv) = env::var("WSLENV") {
            if wslenv.split(':').position(|r| r.eq_ignore_ascii_case("BASH_ENV")).is_some() {
                return false;
            }
        }
    }
    true
}

https://github.com/andy-5/wslgit/blob/master/src/main.rs#L96