The previous patch switched over the content-merge code to use the new
histogram diff code. This patch switches over the content-diff code to
use the histogram diff code. As before, the immediate goal is to speed
it up. `jj diff -r c28ded83fc` in the git.git repo is a good example
of a diff that's extremely slow to calculate with our current
LCS-based diff. With this patch, that drops from 35 s to 0.12 s.
The diff was slightly better before. I think that's mostly because of
our different definition of a "word" in the data. We can improve that
later. The speedup we get now is easily worth the slightly worse diff.
IIUC from rust-lang/rust#81654, `lexical-core` 0.7.4 was broken with
some versions of `rustc` from early February. CI is still failing, so
I guess that is using a `rustc` from that time. However, the logs say
that it installed "rustc 1.53.0-nightly (74874a690 2021-03-30)", so
I'm confused.
I only noticed that there was a newer version when running `cargo
install --path .`, which resulted in warnings about deprecated
functions. There's no other reason I'm aware of to upgrade now.
I'm preparing to publish an early version before someone takes the
name(s) on crates.io. "jj" has been taken by a seemingly useless
project, but "jujube" and "jujube-lib" are still available, so let's
use those.
This adds an interactive mode for `jj restore`. It works by first
creating two temporary directories with the contents of the subset of
files that differ between the two trees, and then letting the user
edit the directory representing the right/after side. This has some
advantages compared to the interactive modes in Git and Mercurial:
* It lets the user edit the final state as opposed to the diff itself
(depending on the diff tool, of course). I think most users find it
easier to edit the file contents than to edit the patch
format.
* It delegates the hard work to a tool that is already written (this
is a big advantage for an immature tool like Jujube, but it is not
an advantage from the user's point of view).
Almost all of the work in this commit went into adding a function that
takes two trees, lets the user edit the diff, and returns a new tree
id. I plan to reuse that function for other interactive commands. One
planned command is `jj edit`, which will let the user edit the changes
in a commit. `jj edit -r abc123` will be mostly about providing a more
intuitive name for `jj restore --source abc123^ --destination abc123`,
plus it will be different for merge commits (it will edit only the
changes in the merge commit). I also plan to add `jj split` by letting
the user edit the full diff, leaving only the parts that should go
into the first commit. Perhaps there will also be commands for moving
part of a commit out of or into a parent commit.
I have never run into this being a problem in practice, but this
change is a stepping stone for two things:
1. Using exponential backoff for other locks (in particular the
working copy).
2. Making the Git store write a ref for conflict objects, so they
don't get GC'd (I want to do that before even I start dogfooding).
I had tried to generate the protobuf code at build time many months
ago, but decided against it because it slowed down the build too
much. I didn't realize there was the
"cargo:rerun-if-changed=<filename>" feature that time. Given that that
exists, it seems like an obvious win to generate the source code at
build time.
I put the generated sources in `$OUT_DIR` (where [1] says they should
be), then include them in the `protos` module by using the `include!`
macro. The biggest problem with that is that I couldn't get IntelliJ
to understand it, even after enabling the experimental features
described in [2].
[1] https://doc.rust-lang.org/cargo/reference/build-script-examples.html#code-generation
[2] https://github.com/intellij-rust/intellij-rust/issues/1908#issuecomment-592773865
