The wasm codebase assumed that clients want to represent text as a
string of characters. This is faster, but in order to enable backwards
compatibility we add a `TextRepresentation` argument to
`automerge_wasm::Automerge::new` to allow clients to choose between a
`string` or `Array<any>` representation. The `automerge_wasm::Observer`
will consult this setting to determine what kind of diffs to generate.
Transactions with no ops in them are generally undesirable. They take up
space in the change log but do nothing else. They are not useless
though, it may occasionally be necessary to create an empty change in
order to list all the current heads of the document as dependents of the
empty change.
The current API makes no distinction between empty changes and non-empty
changes. If the user calls `Transaction::commit` a change is created
regardless of whether there are ops to commit. To provide a more useful
API modify `commit` so that if there is a no-op transaction then no
changes are created, but provide explicit methods to create an empty
change via `Transaction::empty_change`, `Automerge::empty_change` and
`Autocommit::empty_change`. Also make these APIs available in Javascript
and C.
It's tricky to modify these structs with the fields public as every
change requires scanning the codebase for references to make sure you're
not breaking any invariants. Make the fields private to ease
development.
Sometimes it is necessary to query the heads of a document at the time a
transaction started without having a mutable reference to the
transactable. Add `Transactable::base_heads` to do this.
After some discussion with PVH I realise that the repo structure in the
last reorg was very rust-centric. In an attempt to put each language on
a level footing move the rust code and project files into ./rust