fix(git): set GIT_TERMINAL_PROMPT=0 env variable

> If this Boolean environment variable is set to false, git
> will not prompt on the terminal (e.g., when asking for
> HTTP authentication).

As explained by the git docs this prevents private or deleted
repositories from blocking the clone process by asking for
credentials. Unfortunately, this doesn't seem to stop git
from prompting about ssh key authenticity.

src/main.rs

@@ -267,6 +267,7 @@ fn main() -> Result<()> {
                 .arg("clone")
                 .arg(repository.to_string())
                 .arg(&repo_dir)
+                .env("GIT_TERMINAL_PROMPT", "0")
                 .output()?;
             if !out.status.success() {
                 println!("Couldn't clone {} repo status={}", repository, out.status);
@@ -384,6 +385,7 @@ fn main() -> Result<()> {
         let out = Command::new("git")
             .arg("submodule")
             .arg("init")
+            .env("GIT_TERMINAL_PROMPT", "0")
             .current_dir(&repo_dir)
             .output()
             .context("init submodules")?;
@@ -398,6 +400,7 @@ fn main() -> Result<()> {
         let out = Command::new("git")
             .arg("submodule")
             .arg("sync")
+            .env("GIT_TERMINAL_PROMPT", "0")
             .current_dir(&repo_dir)
             .output()
             .context("sync submodules")?;
@@ -412,6 +415,7 @@ fn main() -> Result<()> {
         let out = Command::new("git")
             .arg("submodule")
             .arg("update")
+            .env("GIT_TERMINAL_PROMPT", "0")
             .current_dir(&repo_dir)
             .output()
             .context("update submodules")?;