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: capture-last-use.rs
    path of file: ./repos/cargo/benches/benchsuite/src/bin
    
    the code of the file until where you have to start completion: //! Utility for capturing a global cache last-use database based on the files
//! on a real-world system.
//!
//! This will look in the CARGO_HOME of the current system and record last-use
//! data for all files in the cache. This is intended to provide a real-world
//! example for a benchmark that should be close to what a real set of data
//! should look like.
//!
//! See `benches/global_cache_tracker.rs` for the benchmark that uses this
//! data.
//!
//! The database is kept in git. It usually shouldn't need to be re-generated
//! unless there is a change in the schema or the benchmark.

use cargo::core::global_cache_tracker::{self, DeferredGlobalLastUse, GlobalCacheTracker};
use cargo::util::cache_lock::CacheLockMode;
use cargo::util::interning::InternedString;
use cargo::GlobalContext;
use rand::prelude::SliceRandom;
use std::collections::HashMap;
use std::fs;
use std::fs::File;
use std::io::Write;
use std::path::Path;

fn main() {
    // Set up config.
    let shell = cargo::core::Shell::new();
    let homedir = Path::new(env!("CARGO_MANIFEST_DIR")).join("global-cache-tracker");
    let cwd = homedir.clone();
    let mut gctx = GlobalContext::new(shell, cwd, homedir.clone());
    gctx.configure(
        0,
        false,
        None,
        false,
        false,
        false,
        &None,
        &["gc".to_string()],
        &[],
    )
    .unwrap();
    let db_path = GlobalCacheTracker::db_path(&gctx).into_path_unlocked();
 
    
fn main() {
    // Set up config.
    let shell = cargo::core::Shell::new();
    let homedir = Path::new(env!("CARGO_MANIFEST_DIR")).join("global-cache-tracker");
    let cwd = homedir.clone();
    let mut gctx = GlobalContext::new(shell, cwd, homedir.clone());
    gctx.configure(
        0,
        false,
        None,
        false,
        false,
        false,
        &None,
        &["gc".to_string()],
        &[],
    )
    .unwrap();
    let db_path = GlobalCacheTracker::db_path(&gctx).into_path_unlocked();
    if db_path.exists() {
        fs::remove_file(&db_path).unwrap();
    }

    let _lock = gctx
        .acquire_package_cache_lock(CacheLockMode::DownloadExclusive)
        .unwrap();
    let mut deferred = DeferredGlobalLastUse::new();
    let mut tracker = GlobalCacheTracker::new(&gctx).unwrap();

    let real_home = cargo::util::homedir(&std::env::current_dir().unwrap()).unwrap();

    let cache_dir = real_home.join("registry/cache");
    for dir_ent in fs::read_dir(cache_dir).unwrap() {
        let registry = dir_ent.unwrap();
        let encoded_registry_name = InternedString::new(&registry.file_name().to_string_lossy());
        for krate in fs::read_dir(registry.path()).unwrap() {
            let krate = krate.unwrap();
            let meta = krate.metadata().unwrap();
            deferred.mark_registry_crate_used_stamp(
                global_cache_tracker::RegistryCrate {
                    encoded_registry_name,
                    crate_filename: krate.file_name().to_string_lossy().as_ref().into(),
                    size: meta.len(),
                },
                Some(&meta.modified().unwrap()),
            );
        }
    }

    let mut src_entries = Vec::new();

    let cache_dir = real_home.join("registry/src");
    for dir_ent in fs::read_dir(cache_dir).unwrap() {
        let registry = dir_ent.unwrap();
        let encoded_registry_name = InternedString::new(&registry.file_name().to_string_lossy());
        for krate in fs::read_dir(registry.path()).unwrap() {
            let krate = krate.unwrap();
            let meta = krate.metadata().unwrap();
            let src = global_cache_tracker::RegistrySrc {
                encoded_registry_name,
                package_dir: krate.file_name().to_string_lossy().as_ref().into(),
                size: Some(cargo_util::du(&krate.path(), &[]).unwrap()),
            };
            src_entries.push(src.clone());
            let timestamp = meta.modified().unwrap();
            deferred.mark_registry_src_used_stamp(src, Some(&timestamp));
        }
    }

    let git_co_dir = real_home.join("git/checkouts");
    for dir_ent in fs::read_dir(git_co_dir).unwrap() {
        let git_source = dir_ent.unwrap();
        let encoded_git_name = InternedString::new(&git_source.file_name().to_string_lossy());
        for co in fs::read_dir(git_source.path()).unwrap() {
            let co = co.unwrap();
            let meta = co.metadata().unwrap();
            deferred.mark_git_checkout_used_stamp(
                global_cache_tracker::GitCheckout {
                    encoded_git_name,
                    short_name: co.file_name().to_string_lossy().as_ref().into(),
                    size: Some(cargo_util::du(&co.path(), &[]).unwrap()),
                },
                Some(&meta.modified().unwrap()),
            );
        }
    }

    deferred.save(&mut tracker).unwrap();
    drop(deferred);
    drop(tracker);
    fs::rename(&db_path, homedir.join("global-cache-sample")).unwrap();
    // Clean up the lock file created above.
    fs::remove_file(homedir.join(".package-cache")).unwrap();

    // Save a random sample of crates that the benchmark should update.
    // Pick whichever registry has the most entries. This is to be somewhat
    // realistic for the common case that all dependencies come from one
    // registry (crates.io).
    let mut counts = HashMap::new();
    for src in &src_entries {
        let c: &mut u32 = counts.entry(src.encoded_registry_name).or_default();
        *c += 1;
    }
    let mut counts: Vec<_> = counts.into_iter().map(|(k, v)| (v, k)).collect();
    counts.sort();
    let biggest = counts.last().unwrap().1;

    src_entries.retain(|src| src.encoded_registry_name == biggest);
    let mut rng = &mut rand::thread_rng();
    let sample: Vec<_> = src_entries.choose_multiple(&mut rng, 500).collect();
    let mut f = File::create(homedir.join("random-sample")).unwrap();
    for src in sample {
        writeln!(
            f,
            "{},{},{}",
            src.encoded_registry_name,
            src.package_dir,
            src.size.unwrap()
        )
        .unwrap();
    }
}