With tons of groundwork done, wee can now finally keep the index up to
date within a transaction! That means that we can start relying on the
index to always be valid, so we can use it e.g. for finding common
ancestors within a transaction. That should help speed up `jj evolve`
immensely on large repos.
We still don't write the updated index to disk when the transaction
closes. That will come later.
I want to keep the index updated within the transaction. I tried doing
that by adding a `trait Index`, implemented by `ReadonlyIndex` and
`MutableIndex`. However, `ReadonlyRepo::index` is of type
`Mutex<Option<Arc<IndexFile>>>` (because it is lazily initialized),
and we cannot get a `&dyn Index` that lives long enough to be returned
from a `Repo::index()` from that. It seems the best solution is to
instead create an `Index` enum (instead of a trait), with one readonly
and one mutable variant. This commit starts the migration to that
design by replacing the `Repo` trait by an enum. I never intended for
there there to be more implementations of `Repo` than `ReadonlyRepo`
and `MutableRepo` anyway.
The function used to be larger when we had more reference cycles
between e.g. the `WorkingCopy` and `Repo`. Now there's only
`Evolution` left, so let's inline the function.
This commits makes it so that running commands outside a repo results
in an error message instead of a panic.
We still don't look for a `.jj/` directory in ancestors of the current
directory.
It's annoying to have to have the Git repo and Jujube repo in separate
directories. This commit adds `jj init --git`, which creates a new
Jujube repo with an empty, bare git repo in `.jj/git/`. Hopefully the
`jj git` subcommands will eventually provide enough functionality for
working with the Git repo that the user won't have to use Git commands
directly. If they still do, they can run them from inside `.jj/git/`,
or create a new worktree based on that bare repo.
The implementation is quite straight-forward. One thing to note is
that I made `.jj/store` support relative paths to the Git repo. That's
mostly so the Jujube repo can be moved around freely.
This removes one level of indirection, which is nice because it was
visible to the callers. The `Index` struct is now empty. The next step
is obviously to delete it (and perhaps rename `IndexFile` to `Index`
or `ReadonlyIndex`).
