When building an initial index from an existing Git repo, for example,
we walk parents and predecessors to find all commits to index. Part of
that code was looking up the whole parent and predecessor commits even
though it only needed the ids. I don't know if this has a measurable
impact on performance, but it's not really any more complex to just
get the ids anyway.
Let's acknowledge everyone's contributions by replacing "Google LLC"
in the copyright header by "The Jujutsu Authors". If I understand
correctly, it won't have any legal effect, but maybe it still helps
reduce concerns from contributors (though I haven't heard any
concerns).
Google employees can read about Google's policy at
go/releasing/contributions#copyright.
I'm about to change the index format (to remove predecessor
information), which will break the format. Let's prepare for that by
having `IndexStore` reindex the repo if it fails to read the index..
Unlike the other places I fixed in 134940d2bb, the calls in
`working_copy.rs` should not simply use an existing file if the target
file was open. They should probably try again instead, but I'll leave
that for later.
On Windows, it seems that you can't rename a file if the target file
is open (Stebalien/tempfile#131). I think that's the reason for our
failing tests on Windows. This patch adds a simple wrapper around
`NamedTempFile::persist()` that returns the existing file instead of
failing, if there is one.
This patch introduces a new `IndexStore` struct. The idea is that it
will know about the directory in which the index files are stored, the
associations with operations. It may also cache `Arc<ReadonlyIndex>`
instances so if multiple `ReadonlyIndex` instances are loaded, they
can be returned from the cache. That may be useful when merging
operations because the operations are likely to share a large parent
index file. For now, however, all the new type has is `init()`,
`load()`, and `reinit()`.
