You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: build.rs
    path of file: ./repos/cnosdb/config
    
    the code of the file until where you have to start completion: use std::process::Command;

fn main() {
    let mut 
    
fn main() {
    let mut rustc_env_git_hash = false;
    // Get the GIT_HASH by 'git rev-parse HEAD'.
    // https://stackoverflow.com/questions/43753491/include-git-commit-hash-as-string-into-rust-program
    if let Ok(output) = Command::new("git").args(["rev-parse", "HEAD"]).output() {
        if output.status.success() {
            if let Ok(git_hash) = String::from_utf8(output.stdout) {
                println!("cargo:rustc-env=GIT_HASH={}", git_hash);
                rustc_env_git_hash = true;
            }
        } else {
            eprintln!("Failed to run 'git rev-parse HEAD'");
        }
    } else {
        eprintln!("Failed to start process 'git rev-parse HEAD'");
    }
    if !rustc_env_git_hash {
        // Get the GIT_HASH from environment variable 'CNOSDB_GIT_HASH'
        // when using Github CI to build.
        if let Ok(git_hash) = std::env::var("CNOSDB_GIT_HASH") {
            println!("cargo:rustc-env=GIT_HASH={}", git_hash);
            rustc_env_git_hash = true;
        }
    }
    if !rustc_env_git_hash {
        eprintln!(
            "Failed to get commit hash by 'git rev-parse HEAD' or from env 'CNOSDB_GIT_HASH'"
        );
    }
}