FBShipIt

FBShipIt is a library written in Hack for copying commits from one repository to another.

For example, Meta uses it to:

copy commits from our monolithic Mercurial repository to project-specific GitHub repositories
sync changes from project specific repos like CPython and the linux kernel
Import changes from PyTorch into our Mercurial monorepo

Major Features

read from Git or Mercurial (hg) repositories
write to Git or Mercurial (hg) repositories
remove files or directories matching certain patterns
remove/rewrite sections of commit messages
modify commit authors (for example, if all internal commits are authored by employees, restore original authors for GitHub pull requests)

Major Limitations

FBShipIt has been primarily designed for branches with linear histories; in particular, it does not understand merge commits.

Requirements

Installing

$ composer require facebook/fbshipit

How FBShipIt Works

There are three main concepts: phases, changesets, and filters.

ShipItPhase objects represent a high-level action, such as 'clone this repository', 'pull this repository', 'sync changesets', and 'push repository'.

Within the sync phase, a ShipItChangeset is an immutable object representing a commit.

Filters are functions that take a Changeset, and return a new, modified one.

Provided Phases

ShipItCreateNewRepoPhase: creates a new Git repository with an 'initial commit'. Skipped unless --create-new-repo passed.
ShipItAssertValidFilterPhase: make sure that the filter is consistent with the specified roots.
ShipItGitHubInitPhase: create and configure a github clone.
ShipItPullPhase: pull in any new changes to a repository.
ShipItPushPhase: push local changes to the destination repository.
ShipItSyncPhase: copy commits from the source repository to the destination repository.
ShipItVerifyRepoPhase: check that the destination repository matches the source repository and filter. Skipped unless --verify or --create-fixup-patch is passed.

Using FBShipIt

You need to construct:

a ShipItManifest object, defining your default working directory, and the directory names of your source and destination repositories
a list of phases you want to run
a pipeline of filters, assuming you are using the ShipItSyncPhase

Filters are provided for common operations - the most frequent are:

ShipItPathFilters::moveDirectories(string $changeset, dict<string, string> $mapping): apply patches to a different directory in the destination repository
ShipItPathFilters::stripPaths(string $changeset, vec<string> $patterns, vec<string> $exception_patterns = vec[]): remove any modifications to paths matching $patterns, unless they match something in $exception_patterns.

Example

See the demo/ directory for a simple example to start from.

Using With An Empty Destination Repository

Add ShipItCreateNewRepoPhase to your phase list (after source init and pull phases), then run:

hhvm my_script.hack --create-new-repo

This will give you the path to a git repository with a single commit; you can then push it to your destination.

Using With An Existing Destination Repository

When there is at least one relevant commit in the source repository that is not in the destination repository, run:

hhvm my_script.hack --first-commit=FIRST_UNSYNCED_COMMIT_ID_GOES_HERE

Future Runs

Run your script with no arguments; FBShipIt adds tracking information to the commits it creates, so will automatically sync any new commits.

Reducing Common Code With Multiple Projects

We recommend splitting out common filters and phase setup to separate classes, and for these to be re-used between your projects. For an example from Facebook's usage, see FBCommonFilters

Further Examples

Some other code that might be useful for configuring FBShipIt can be found in fb-examples/.

License

FBShipIt is MIT-licensed.

facebook / fbshipit