mirror of
https://github.com/splitsh/lite.git
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167 lines
5.5 KiB
Markdown
167 lines
5.5 KiB
Markdown
Git Subtree Splitter
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====================
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**splitsh-lite** replaces the `subtree split` Git built-in command to make
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**splitting a monolithic repository** to read-only standalone repositories
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**easy and fast**.
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Why do I need this tool?
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------------------------
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When starting a project, do you store all the code in one repository? Or are
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you creating many standalone repositories?
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Both strategies work well and both have drawbacks as well. **splitsh** helps
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use both strategies by providing tools that automatically **synchronize a
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monolithic repository to standalone repositories** in real-time.
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**splitsh-lite** is a sub-project that provides a faster implementation of the
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`git subtree split` command, which helps create standalone repositories for one
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or more sub-directories of a main repository.
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If you want to learn more about monorepo vs manyrepos, watch this [4-minute
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lightning talk](http://www.thedotpost.com/2016/05/fabien-potencier-monolithic-repositories-vs-many-repositories)
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I gave at dotScale
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(or [read the slides](https://speakerdeck.com/fabpot/a-monorepo-vs-manyrepos))...
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or watch the longer version from
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[DrupalCon](https://www.youtube.com/watch?v=4w3-f6Xhvu8).
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["The Monorepo - Storing your source code has never been so much fun"](https://speakerdeck.com/garethr/the-monorepo-storing-your-source-code-has-never-been-so-much-fun)
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is also a great resource.
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**Note** If you currently have multiple repositories that you want to merge into
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a monorepo, use the [tomono](https://github.com/unravelin/tomono) tool.
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Installation
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------------
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Manual Installation
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-------------------
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First, you need to install `libgit2`, preferably using your package manager of
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choice.
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If you get `libgit2` version `1.5`, you're all set and jump to the compilation
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step below. If not, you first need to change the `git2go` version used in the
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code. Using the table on the
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[libgit2](https://github.com/libgit2/git2go#which-go-version-to-use) repository,
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figure out which version of the `git2go` you need based on the `liggit2` library
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you installed. Let's say you need version `v31`:
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```bash
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sed -i -e 's/v34/v31/g' go.mod splitter/*.go
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go mod tidy
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```
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Then, compile `splitsh-lite`:
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```bash
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go build -o splitsh-lite github.com/splitsh/lite
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```
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If everything goes fine, a `splitsh-lite` binary should be available in the
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current directory.
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If you get errors about an incompatible `libgit2` library, try exporting the
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needed flags, e.g.
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```bash
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export LDFLAGS="-L/opt/homebrew/opt/libgit2@1.5/lib"
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export CPPFLAGS="-I/opt/homebrew/opt/libgit2@1.5/include"
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export PKG_CONFIG_PATH="/opt/homebrew/opt/libgit2@1.5/lib/pkgconfig"
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```
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before running `go build`.
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If you want to integrate splitsh with Git, install it like this (and use it via
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`git splitsh`):
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```bash
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cp splitsh-lite "$(git --exec-path)"/git-splitsh
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```
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Usage
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-----
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Let's say you want to split the `lib/` directory of a repository to its own
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branch; from the "master" Git repository (bare or clone), run:
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```bash
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splitsh-lite --prefix=lib/
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```
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The *sha1* of the split is displayed at the end of the execution:
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```bash
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SHA1=`splitsh-lite --prefix=lib/`
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```
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The sha1 can be used to create a branch or to push the commits to a new
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repository.
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Automatically create a branch for the split by passing a branch name
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via the `--target` option:
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```bash
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splitsh-lite --prefix=lib/ --target=heads/branch-name
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```
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If new commits are made to the repository, update the split by running the same
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command again. Updates are much faster as **splitsh-lite** keeps a cache of
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already split commits. Caching is possible as **splitsh-lite** guarantees that
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two splits of the same code always results in the same history and the same
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`sha1`s for each commit.
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By default, **splitsh-lite** splits the currently checked out branch but you can
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split a different branch by passing it explicitly via the `--origin` flag
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(mandatory when splitting a bare repository):
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```bash
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splitsh-lite --prefix=lib/ --origin=origin/master
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```
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You don't even need to run the command from the Git repository directory if you
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pass the `--path` option:
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```bash
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splitsh-lite --prefix=lib/ --origin=origin/1.0 --path=/path/to/repo
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```
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Available options:
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* `--prefix` is the prefix of the directory to split; the value can be one of
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the following:
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* `from`: the origin directory to split;
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* `from:to`: move the split content to a sub-directory on the target;
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* `from:to:exclude`: exclude a directory from the origin `from` directory
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(use `from:to:exclude1:exclude2:...` to exclude more than one
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directory).
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Split several directories by passing multiple `--prefix` flags;
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* `--path` is the path of the repository to split (current directory by default);
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* `--origin` is the Git reference for the origin (can be any Git reference
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like `HEAD`, `heads/xxx`, `tags/xxx`, `origin/xxx`, or any `refs/xxx`);
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* `--target` creates a reference for the tip of the split (can be any Git
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reference like `heads/xxx`, `tags/xxx`, `origin/xxx`, or any `refs/xxx`);
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* `--progress` displays a progress bar;
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* `--scratch` flushes the cache (useful when a branch is force pushed or in
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case of a cache corruption).
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Migrating from `git subtree split`
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----------------------------------
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Migrating from `git subtree split` to `splith-lite` is easy as both tools
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generate the same `sha1`s.
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However, note that older versions of `git subtree split` used broken
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algorithms, and so generated different `sha1`s than the latest version. You can
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simulate those version via the `--git` flag. Use `<1.8.2` or `<2.8.0` depending
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on which version of `git subtree split` you want to simulate.
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