List all commits and files changed between commits

[vbrandl]

Hey

I'm trying to use git-repository to iterate over all commits from HEAD and get the files that changed between commits:

#[derive(Debug)]
struct Change {
    author: String,
    message: String,
    filenames: HashSet<String>,
}

fn id_to_commit(id: Id) -> Result<Commit> {
    let object = id.try_object()?;
    let object = object.expect("empty");
    let commit = object.try_into_commit()?;
    Ok(commit)
}

fn load_history(path: impl AsRef<Path>) -> Result<History> {
    let repo = git_repository::discover(path)?;
    let rev_walk = repo.rev_walk(Some(repo.head_id()?.detach()));
    let mut changes = rev_walk
        .all()?
        .filter_map(Result::ok)
        .map(id_to_commit)
        .filter_map(Result::ok);
    let mut last = changes.next().unwrap();
    let mut result = Vec::new();
    for next in changes {
        result.push(change_from_commit(&last, Some(&next))?);
        last = next;
    }

    // TODO: once again with last
    // result.push(change_from_commit(&last, None));

    Ok(History(result))
}

fn change_from_commit(last: &Commit, next: Option<&Commit>) -> Result<Change> {
    let author = last.author()?;
    let author = format!("{} <{}>", author.name, author.email);
    let message = last.message()?;
    let message = format!(
        "{}",
        message.title.to_os_str()?.to_string_lossy().trim_end()
    );

    let tree = if let Some(next) = next {
        next.tree()?
    } else {
        todo!("empty tree?")
    };
    let mut changes = tree.changes();
    let changes = changes.track_path();
    let last_tree = last.tree().unwrap();
    let mut filenames = HashSet::new();
    changes.for_each_to_obtain_tree(&last_tree, |change| {
        let is_file_change = match change.event {
            Event::Addition { entry_mode, .. } => entry_mode == EntryMode::Blob,
            Event::Modification { entry_mode, .. } => entry_mode == EntryMode::Blob,
            Event::Deletion { .. } => false,
        };
        if is_file_change {
            let path = change.location.to_os_str()?.to_string_lossy();
            filenames.insert(format!("{}", path));
        }

        Ok::<Action, Utf8Error>(Action::Continue)
    })?;
    Ok(Change {
        author,
        message,
        filenames,
    })
}

This works fine until the initial commit where I can't get a Tree to compare to. git_objects::objs::Tree::empty() is not compatible. How can I get the diff for the initial commit?

[Byron]

Here is how an empty tree of the correct type can be obtained by hand:

        repo.find_object(git::hash::ObjectId::empty_tree(repo.object_hash()))
            .expect("always present")
            .into_tree()

Just now I also added a new method, Repository::empty_tree() to do exactly that.
I hope that helps.