Finish cat-file command implementation

Compiler is not happy yet. Because we added a new entry to Command enum but we didn't add it to match expression in main.rs.

Let's add it:

src/main.rs

fn main() -> Result<()> {
    let command = parse_args().unwrap();
    match command {
        Command::Init { path } => {
            GitRepository::create(path)?;
        }
        Command::CatFile {
            object_type,
            object_hash,
        } => {
            cmd_cat_file(object_type, object_hash)?;
        }
    };

    Ok(())
}

If the parsed command is CatFile we call cmd_cat_file:

src/main.rs

fn cmd_cat_file(object_type: git_object::GitObjectType, object_hash: String) -> Result<()> {
    let current_directory = std::env::current_dir()?;
    let repo = GitRepository::find(&current_directory)?;

    let object = git_object::read(&repo, repo.find_object(object_type, object_hash))?;
    print!("{}", object.serialize()); // Don't use println! here
    Ok(())
}

First, we get the directory in which the command is executed. Then we create a new GitRepository object using this path. We use find function in order to find the repo.

Then in line 5 we read the object and print the result in line 6. Here we introduced yet another auxiliary function named find_object in GitRepository struct:

src/repository.rs

    pub fn find_object(&self, _object_type: git_object::GitObjectType, name: String) -> String {
        name
    }

Why do we need this function?

The reason for this strange small function is that Git has a lot of ways to refer to objects: full hash, short hash, tags… object_find() will be our name resolution function. We’ll only implement it later, so this is just a temporary placeholder (so our code can run already, without the real version). This means that until we implement the real thing, the only way we can refer to an object will be by its full hash.[source]