e86d266e6b
I'm trying to replace the Git backend's use of Git notes for storing metadata (#7). This patch adds a file format that I hope can be used for that. It's a simple generic format for storing fixed-size keys and associated variable-size values. The keys are stored in sorted order. Each key is followed by an offset to the value. The offset is relative to the first value. All values are concatenated after each other. I suppose it's a bit like Git's pack files but lacking both delta-encoding and compression. Each file can also have a parent pointer (just like the index files have), so we don't have to rewrite the whole file each time. As with the index files, the new format squashes a file into its parent if it contains more than half the number of entries of the parent. The code is also based on `index.rs`. Perhaps we can alo replace the default operation storage with this format. Maybe also the native local backend's storage. We'll need delta-encoding and compression soon then. |
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Jujutsu
Disclaimer
This is not a Google product. It is an experimental version-control system (VCS). It was written by me, Martin von Zweigbergk (martinvonz@google.com). It is my personal hobby project. It does not indicate any commitment or direction from Google.
Introduction
I started the project mostly in order to test the viability of some UX ideas in practice. I continue to use it for that, but my short-term goal now is to make it useful as an alternative CLI for Git repos.
The command-line tool is called jj for now because it's easy to type and easy
to replace (rare in English). The project is called "Jujutsu" because it matches
"jj" (I initially called it "Jujube", but changed since jujutsu is more
well-known).
Features:
-
Compatible with Git
Jujutsu has two backends. One of them is a Git backend (the other is a native one). This lets you use Jujutsu as an alternative interface to Git. The commits you create will look like regular Git commits. You can always switch back to Git.
-
The working copy is automatically committed
Most Jujutsu commands automatically commit the working copy. This leads to a simpler and more powerful interface, since all commands work the same way on the working copy or any other commit. It also means that you can always check out a different commit without first explicitly committing the working copy changes (you can even check out a different commit while resolving merge conflicts).
-
Operations update the repo first, then possibly the working copy
The working copy is only updated at the end of an operation, after all other changes have already been recorded. This means that you can run any command (such as
jj rebase) even if the working copy is dirty. -
Entire repo is under version control
All operations you perform in the repo are recorded, along with a snapshot of the repo state after the operation. This means that you can easily revert to an earlier repo state, or to simply undo a particular operation (which does not necessarily have to be the most recent operation).
-
Conflicts can be recorded in commits
If an operation results in conflicts, information about those conflicts will be recorded in the commit(s). The operation will succeed. You can then resolve the conflicts later. One consequence of this design is that there's no need to continue interrupted operations. Instead, you get a single workflow for resolving conflicts, regardless of which command caused them. This design also lets Jujutsu rebase merge commits correctly (unlike both Git and Mercurial).
-
Automatic rebase
Whenever you modify a commit, any descendants of the old commit will be rebased onto the new commit. Thanks to the conflict design described above, that can be done even if there are conflicts. Branches pointing to rebased commits will be updated. So will the working copy if it points to a rebased commit.
Status
The tool is quite feature-complete. I have almost exclusively used jj to
develop the project itself since early January 2021. However, there will be
changes to workflows and backward-incompatible changes to the on-disk formats
(I'll try to provide upgrade commands if requested). It's also likely that
workflows and setups different from what I personally use are not well
supported.
Installation
# We need the "nightly" Rust toolchain. This command installs that without
# changing your default.
$ rustup install nightly
$ cargo +nightly install --git https://github.com/martinvonz/jj.git
To set up command-line completion, source the output of
jj debug completion --bash/--zsh/--fish. For example, if you use Bash:
$ source <(jj debug completion) # --bash is the default
You may also want to configure your name and email so commits are made in your
name. Create a ~/.jjconfig file and make it look something like this:
$ cat ~/.jjconfig
[user]
name = "Martin von Zweigbergk"
email = "martinvonz@google.com"
Getting started
The best way to get started is probably to go through the tutorial.