That way, the head is static which allows to re-use the worktree status across
multiple related calls.
Also, add a way to quickly get the `head_commit()` from a `git2::Repository`.
Note that this may cause breakage in the app, as now it will see the actual
head, not a computed one, but that should also help us to find places that
didn't properly update their state.
The worktree diff is essentially a 'git status' with a given tree,
and that can be expressed with a diff of the workdir, the index and a tree.
This comes at the expense of not being able to control which file sizes are diffed.
This is a change in perception, as `given_name()` was the name of a virtual-branch,
which is also used to correlate other similarly named branches.
Thus, it's now more than just that, and for lack of a better word it's called
the 'identity' of a branch.
It's something very specific and shouldn't accidentally be used wrongly, hence
the strong typing.
This also needs the ability to create commits.
Also experiment with `async` tauri commands, but without actually making
them `async` - nothing actually is so why pretend?
Further, assure we get the correct author and committer which helps it
pick up the overridden author information when creating a commit.
That way it's assured that reads and writes don't intersect, but assure we only
hold such lock for the shortest amount of time for reads and and for the
full duration of writes.
* use `ctx` as name instead of `project_repository` to make lines shorter
and more readable. This could be done everywhere once the type-name changes
as well.
* Where possible, avoid using `&self` for `VirtualBranchActions` as there is no state.
For now I avoided to remove its usage as field in the filesystem monitor.
* Use a more modern way to use state in `tauri` commands.
* Add the `Ext` suffix to what clearly is extension traits.
Further to the move - the VirtualBranchesExt trait creates a dependency towards gitbutler-project. The gitubler-branch crate doesn't have such dependency so i deemed it undesirable to introduce it just for a convinience method.
(Separately added an extention in gitbutler-virtual-actions since it already depends on project and to create a smaller diff)
