diff --git a/README.md b/README.md index 130be094b7..9fe869c533 100644 --- a/README.md +++ b/README.md @@ -23,21 +23,103 @@ ## Introduction -Jujutsu is a -[Git-compatible](https://martinvonz.github.io/jj/latest/git-compatibility) -[DVCS](https://en.wikipedia.org/wiki/Distributed_version_control). It combines -features from Git (data model, -[speed](https://github.com/martinvonz/jj/discussions/49)), Mercurial (anonymous -branching, simple CLI [free from "the -index"](https://martinvonz.github.io/jj/latest/git-comparison#the-index), -[revsets](https://martinvonz.github.io/jj/latest/revsets), powerful -history-rewriting), and Pijul/Darcs ([first-class -conflicts](https://martinvonz.github.io/jj/latest/conflicts)), with features not -found in most of them -([working-copy-as-a-commit](https://martinvonz.github.io/jj/latest/working-copy), -[undo functionality](https://martinvonz.github.io/jj/latest/operation-log), -automatic rebase, [safe replication via `rsync`, Dropbox, or distributed file -system](https://martinvonz.github.io/jj/latest/technical/concurrency)). +Jujutsu is a powerful [version control system](https://en.wikipedia.org/wiki/Version_control) +for software projects. You use it to get a copy of your code, track changes +to the code, and finally publish those changes for others to see and use. +It is designed from the ground up to be easy to use—whether you're new or +experienced, working on brand new projects alone, or large scale software +projects with large histories and teams. + +Jujutsu is unlike most other systems, because internally it abstracts the user +interface and version control algorithms from the *storage systems* used to +serve your content. This allows it to serve as a VCS with many possible physical +backends, that may have their own data or networking models—like [Mercurial] or +[Breezy], or hybrid systems like Google's cloud-based design, [Piper/CitC]. + +[Mercurial]: https://www.mercurial-scm.org/ +[Breezy]: https://www.breezy-vcs.org/ +[Piper/CitC]: https://youtu.be/W71BTkUbdqE?t=645 + +Today, we use Git repositories as a storage layer to serve and track content, +making it **compatible with many of your favorite Git-based tools, right now!** +All core developers use Jujutsu to develop Jujutsu, right here on GitHub. But it +should hopefully work with your favorite Git forges, too. + +We combine many distinct design choices and concepts from other version control +systems into a single tool. Some of those sources of inspiration include: + +- **Git**: We make an effort to [be fast][perf]—with a snappy UX, efficient + algorithms, correct data structures, and good-old-fashioned attention to + detail. The default storage backend uses Git repositories for "physical + storage", for wide interoperability and ease of onboarding. + +- **Mercurial & Sapling**: There are many Mercurial-inspired features, such as + the [revset] language to select commits. There is [no explicit index][no-index] + or staging area. Branches are "anonymous" like Mercurial, so you don't need + to make up a name for each small change. Primitives for rewriting history are + powerful and simple. Formatting output is done with a robust template language + that can be configured by the user. + +- **Pijul & Darcs**: Jujutsu keeps track of conflicts as [first-class objects][conflicts] + in its model; they are first-class in the same way commits are, while + alternatives like Git simply think of conflicts as textual diffs. While not + as rigorous as based systems like Darcs and Pijul (which are based on + a formalized theory of patches, as opposed to snapshots), the effect is + that many forms of conflict resolution can be performed and propagated + automatically. + +[perf]: https://github.com/martinvonz/jj/discussions/49 +[revset]: https://martinvonz.github.io/jj/latest/revsets/ +[no-index]: https://martinvonz.github.io/jj/latest/git-comparison/#the-index +[conflicts]: https://martinvonz.github.io/jj/latest/conflicts/ + +And it adds several innovative, useful features of its own: + +- **Working-copy-as-a-commit**: Changes to files are [recorded automatically][wcc] + as normal commits, and amended on every subsequent change. This "snapshot" + design simplifies the user-facing data model (commits are the only visible + object), simplifies internal algorithms, and completely subsumes features like + Git's stashes or the index/staging-area. + +- **Operation log & undo**: Jujutsu records every operation that is performed on the + repository, from commits, to pulls, to pushes. This makes debugging problems like + "what just happened?" or "how did I end up here?" easier, *especially* when + you're helping your coworker answer those questions about their repository! + And because everything is recorded, you can undo that mistake you just made + with ease. Version control has finally entered [the 1960s][undo-history]! + +- **Automatic rebase and conflict resolution**: When you modify a commit, every + descendent is automatically rebased on top of the freshly-modified one. This + makes "patch-based" workflows a breeze. If you resolve a conflict in a commit, + the _resolution_ of that conflict is also propagated through descendants as + well. In effect, this is a completely transparent version of `git rebase + --update-refs` combined with `git rerere`, supported by design. + + > [!WARNING] + > The following features are available for use, but experimental; they may + > have bugs, backwards incompatible storage changes, and user-interface + > changes! + +- **Safe, concurrent replication**: Have you ever wanted to store your version + controlled repositories inside a Dropbox folder? Or continuously backup + repositories to S3? No? Well, now you can! + + The fundamental problem with using filesystems like Dropbox and backup tools + like `rsync` on your typical Git/Mercurial repositories is that that they rely + on *local filesystem operations* being atomic, serialized, and non-concurrent + with respect to other reads and writes—which is _not_ true when operating on + distributed file systems, or when operations like concurrent file copies (for + backup) happen while lock files are being held. + + Jujutsu is instead designed to be [safe under concurrent scenarios][conc-safety]; + simply using rsync or Dropbox and then using that resulting repository + should never result in a repository in a *corrupt state*. The worst that + _should_ happen is that it will expose conflicts between the local and remote + state, leaving you to resolve them. + +[wcc]: https://martinvonz.github.io/jj/latest/working-copy/ +[undo-history]: https://en.wikipedia.org/wiki/Undo#History +[conc-safety]: https://martinvonz.github.io/jj/latest/technical/concurrency/ 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 @@ -49,14 +131,11 @@ questions, or want to talk about future plans, please join us on Discord or start a [GitHub Discussion](https://github.com/martinvonz/jj/discussions); the developers monitor both channels. -> [!IMPORTANT] -> Jujutsu is an **experimental version control system**. While Git compatibility -> is stable, and most developers use it daily for all their needs, there may -> still be work-in-progress features, suboptimal UX, and workflow gaps that make -> it unusable for your particular use. - ### News and Updates 📣 +- **Oct 2023**: Version 0.10.0 is released! Now includes a bundled merge and + diff editor for all platforms, "immutable revsets" to avoid accidentally + `edit`-ing the wrong revisions, and lots of polish. - **Jan 2023**: Martin gave a presentation about Google's plans for Jujutsu at Git Merge 2022! See the [slides](https://docs.google.com/presentation/d/1F8j9_UOOSGUN9MvHxPZX_L4bQ9NMcYOp1isn17kTC_M/view) @@ -64,6 +143,12 @@ developers monitor both channels. ## Getting started +> [!IMPORTANT] +> Jujutsu is an **experimental version control system**. While Git compatibility +> is stable, and most developers use it daily for all their needs, there may +> still be work-in-progress features, suboptimal UX, and workflow gaps that make +> it unusable for your particular use. + Follow the [installation instructions](https://martinvonz.github.io/jj/latest/install-and-setup) to obtain and configure `jj`. @@ -89,17 +174,22 @@ the header of the website when you scroll to the top of any page. ### Compatible with Git -Jujutsu has two -[backends](https://martinvonz.github.io/jj/latest/glossary#backend). One of them -is a Git backend (the other is a native one [^native-backend]). 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 Git support -uses the [libgit2](https://libgit2.org/) C library. +Jujutsu is designed so that the underlying data and storage model is abstract. +Today, it features two [backends]—one of them uses a Git repository for storage, +while the other is a native storage backend[^native-backend]. + +[backends]: https://martinvonz.github.io/jj/latest/glossary#backend [^native-backend]: At this time, there's practically no reason to use the native backend. The backend exists mainly to make sure that it's possible to eventually add functionality that cannot easily be added to the Git backend. +The Git backend is fully featured and maintained, and allows you to 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 Git support uses the +[libgit2](https://libgit2.org/) C library. + + You can even have a ["co-located" local @@ -179,12 +269,14 @@ commit to any other commit using `jj move`. The tool is fairly feature-complete, but some important features like (the equivalent of) `git blame` are not yet supported. There -are also several performance bugs. It's also likely that workflows and setups -different from what the core developers use are not well supported. - -I (Martin von Zweigbergk) have almost exclusively used `jj` to develop the -project itself since early January 2021. I haven't had to re-clone from source -(I don't think I've even had to restore from backup). +are also several performance bugs. It's likely that workflows and setups +different from what the core developers use are not well supported, e.g. there +is no native support for email-based workflows. + +Today, all core developers use `jj` to work on `jj`. I (Martin von Zweigbergk) +have almost exclusively used `jj` to develop the project itself since early +January 2021. I haven't had to re-clone from source (I don't think I've even had +to restore from backup). There *will* be changes to workflows and backward-incompatible changes to the on-disk formats before version 1.0.0. Even the binary's name may change (i.e.