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https://github.com/splitsh/lite

Split a repository to read-only standalone repositories
https://github.com/splitsh/lite

git monolithic monorepo split subtree synchronization

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Split a repository to read-only standalone repositories

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README 

        
Git Subtree Splitter

====================



**splitsh-lite** replaces the `subtree split` Git built-in command to make

**splitting a monolithic repository** to read-only standalone repositories

**easy and fast**.



Why do I need this tool?

------------------------



When starting a project, do you store all the code in one repository? Or are

you creating many standalone repositories?



Both strategies work well and both have drawbacks as well. **splitsh** helps

use both strategies by providing tools that automatically **synchronize a

monolithic repository to standalone repositories** in real-time.



**splitsh-lite** is a sub-project that provides a faster implementation of the

`git subtree split` command, which helps create standalone repositories for one

or more sub-directories of a main repository.



If you want to learn more about monorepo vs manyrepos, watch this [4-minute

lightning talk](http://www.thedotpost.com/2016/05/fabien-potencier-monolithic-repositories-vs-many-repositories)

I gave at dotScale

(or [read the slides](https://speakerdeck.com/fabpot/a-monorepo-vs-manyrepos))...

or watch the longer version from

[DrupalCon](https://www.youtube.com/watch?v=4w3-f6Xhvu8).

["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)

is also a great resource.



**Note** If you currently have multiple repositories that you want to merge into

a monorepo, use the [tomono](https://github.com/unravelin/tomono) tool.



Installation

------------



Manual Installation

-------------------



First, you need to install `libgit2`, preferably using your package manager of

choice.



If you get `libgit2` version `1.5`, you're all set and jump to the compilation

step below. If not, you first need to change the `git2go` version used in the

code. Using the table on the

[libgit2](https://github.com/libgit2/git2go#which-go-version-to-use) repository,

figure out which version of the `git2go` you need based on the `liggit2` library

you installed. Let's say you need version `v31`:



```bash

sed -i -e 's/v34/v31/g' go.mod splitter/*.go

go mod tidy

```



Then, compile `splitsh-lite`:



```bash

go build -o splitsh-lite github.com/splitsh/lite

```



If everything goes fine, a `splitsh-lite` binary should be available in the

current directory.



If you get errors about an incompatible `libgit2` library, try exporting the

needed flags, e.g.



```bash

export LDFLAGS="-L/opt/homebrew/opt/[email protected]/lib"

export CPPFLAGS="-I/opt/homebrew/opt/[email protected]/include"

export PKG_CONFIG_PATH="/opt/homebrew/opt/[email protected]/lib/pkgconfig"

```



before running `go build`.



If you want to integrate splitsh with Git, install it like this (and use it via

`git splitsh`):



```bash

cp splitsh-lite "$(git --exec-path)"/git-splitsh

```



Usage

-----



Let's say you want to split the `lib/` directory of a repository to its own

branch; from the "master" Git repository (bare or clone), run:



```bash

splitsh-lite --prefix=lib/

```



The *sha1* of the split is displayed at the end of the execution:



```bash

SHA1=`splitsh-lite --prefix=lib/`

```



The sha1 can be used to create a branch or to push the commits to a new

repository.



Automatically create a branch for the split by passing a branch name

via the `--target` option:



```bash

splitsh-lite --prefix=lib/ --target=heads/branch-name

```



If new commits are made to the repository, update the split by running the same

command again. Updates are much faster as **splitsh-lite** keeps a cache of

already split commits. Caching is possible as **splitsh-lite** guarantees that

two splits of the same code always results in the same history and the same

`sha1`s for each commit.



By default, **splitsh-lite** splits the currently checked out branch but you can

split a different branch by passing it explicitly via the `--origin` flag

(mandatory when splitting a bare repository):



```bash

splitsh-lite --prefix=lib/ --origin=origin/master

```



You don't even need to run the command from the Git repository directory if you

pass the `--path` option:



```bash

splitsh-lite --prefix=lib/ --origin=origin/1.0 --path=/path/to/repo

```



Available options:



 * `--prefix` is the prefix of the directory to split; the value can be one of

   the following:



     * `from`: the origin directory to split;



     * `from:to`: move the split content to a sub-directory on the target;



     * `from:to:exclude`: exclude a directory from the origin `from` directory

       (use `from:to:exclude1:exclude2:...` to exclude more than one

       directory).



   Split several directories by passing multiple `--prefix` flags;



 * `--path` is the path of the repository to split (current directory by default);



 * `--origin` is the Git reference for the origin (can be any Git reference

   like `HEAD`, `heads/xxx`, `tags/xxx`, `origin/xxx`, or any `refs/xxx`);



 * `--target` creates a reference for the tip of the split (can be any Git

   reference like `heads/xxx`, `tags/xxx`, `origin/xxx`, or any `refs/xxx`);



 * `--progress` displays a progress bar;



 * `--scratch` flushes the cache (useful when a branch is force pushed or in

   case of a cache corruption).



Migrating from `git subtree split`

----------------------------------



Migrating from `git subtree split` to `splith-lite` is easy as both tools

generate the same `sha1`s.



However, note that older versions of `git subtree split` used broken

algorithms, and so generated different `sha1`s than the latest version. You can

simulate those version via the `--git` flag. Use `<1.8.2` or `<2.8.0` depending

on which version of `git subtree split` you want to simulate.