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Christian Edward Gruber edited this page May 13, 2015 · 2 revisions

Why Moe?

MOE helps one project live in two repositories. If you only ever want your code to be used in one repository, you should stop reading now.

Why is this Hard?

Some people know how to command git or mercurial to dance to their command, and have no need for MOE.

MOE is useful in the face of:

  • users who are not git/hg wizards
  • source control system heterogeneity
  • having differences between the internal and public codebases. This last reason gives rise to the concept of Project Spaces

Concepts

With MOE, you describe your project's two Repositories:

A Repository is a source control repository that stores your project. It offers:

  • a way to get metadata about what has happened in that repository
  • a way to construct a Codebase at a revision.

A Codebase is a set of files with their contents and metadata (for now, only their executable bits).

We assume that these repositories are in different ProjectSpace s: i.e., they should always be different. (For background on why this might be useful, check out ProjectSpace s).

A Translator takes a Codebase in one ProjectSpace and creates a Codebase in another ProjectSpace. The Identity Translator does nothing (in the case that you expect the two ProjectSpace s to always be equal). More complex translators like the ScrubberInvokingTranslator and UndoScrubbingTranslator (which will exist soon) allow you to maintain differences.

A Revision is known in each Repository by a different name (a changeset in mercurial; a revision in subversion; a commit in git, etc.).

A Migration is an attempt to take code from one Repository (at one Revision) and move it to another Revision. This may include attempting to translate it (via a translator) and copy metadata (such as a Revision description, or author, or time/data of commit), and submit it to another Repository.

MOE is a toolkit for acting on these concepts.

What Next

If you don't know anyone else using MOE, it sounds like you're using MOE at a new site. See NewMoeSite .

If your site is already using moe, then see SetUpMoe to get your project up to speed.

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