Automatically fetch your project’s dependencies with gb

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gb has been in development for just over a year now. Since the announcement in May 2015 the project has received over 1,600 stars, produced 16 releases, and attracted 41 contributors.

Thanks to a committed band of early adopters, gb has grown to be a usable day to day replacement for the go tool. But, there is one area where gb has not lived up to my hopes, and that is dependency management.

gb’s $PROJECT/vendor/ directory was the inspiration for the go tool’s vendor/ directory (although their implementations differ greatly) and has delivered on its goal of reproducible builds for Go projects. However, the success of gb’s project based model, and vendoring code in general, has a few problems. Specifically, wholesale copying (or forking if you prefer) of one code base into another continues to sidestep the issue of adoption of a proper release and versioning culture amongst Go developers.

To be fair, for Go developers using the tools they have access to today–including gb–there is no incentive to release their code. As a Go package author, you get no points for doing proper versioned releases if your build tool just pulls from HEAD anyway. There is similarly limited value in adopting a version numbering policy like SemVer if your tools only memorise the git revision you last copied your code at.

A second problem, equally poorly served by gb or the vendor/ support in the go tool, are developers and projects who cannot, usually for legal reasons, or do not wish to, copy code wholesale into their project. Suggestions of using git submodules have been soundly dismissed as unworkable.

With the release of gb 0.4.3, there is a new way to manage dependencies with gb. This new method does not replace gb vendor or $PROJECT/vendor as the recommended method for achieving reproducible builds, but it does acknowledge that vendoring is not appropriate for all use cases.

To be clear, this new mode of managing dependencies does not supersede or deprecate the existing mechanisms of cloning source code into $PROJECT/vendor. The automatic download feature is optional and is activated by the project author creating a file in their project’s root called, $PROJECT/depfile.

If you have a gb project that is currently vendoring code, or you’re using gb vendor restore to actively avoid cloning code into your project, you can try this feature today, with the following caveats:

1. Currently only GitHub is supported. This is because the new facility uses the GitHub API to download release tarballs via https. Vanity urls that redirect to GitHub are also not supported yet, but will be supported soon.
2. The repository must have made a release of its code, and that release must be tagged with a tag containing a valid SemVer 2.0.0 version number. The format of the tag is described in this proposal. If a dependency you want to consume in your gb project has not released their code, then please ask them to do so.

Polishing this feature will be the remainder of the 0.4.x development series. After this work is complete gb vendor will be getting some attention. Ultimately both gb vendor and $PROJECT/depfile do the same thing–one copies the source of your dependencies into your project, the other into your home directory.