16 Jun 2016

Overriding Repositories In repo Manifests With Personal Github Forks

Here is the situation: you're working on a development project that uses repo[1] but you'd like to replace one or more of those repositories with ones of your own which you have forked on github and would like to be able to push your changes back into your github fork.

The good news is repo already has a mechanism for this. The only complicated part is getting the github URL correct such that you can push your changes via ssh.

 In the project's manifest will be a repository you want to override; it has a name. In your project go into the .repo directory and create a directory called local_manifests. In .repo/local_manifests create a file using any filename, just make sure it ends with .xml ; for some, unknown reason, it is traditional to name this file roomservice.xml . Within .repo/local_manifests/roomservice.xml you can remove and add repositories to your heart's content.

For example, the project I'm working on has a manifest that looks like:
  1 <?xml version="1.0" encoding="UTF-8"?>
  2 <manifest>
  3     <default revision="master" sync-j="4"/>
  4
  5     <remote fetch="http://github.com/" name="github"/>
  6     <remote fetch="http://github.com/insane-adding-machines/" name="frosted"/>
  7     <remote fetch="git://crosstool-ng.org/" name="crosstool-ng"/>
  8
  9     <!-- utilities -->
 10     <project remote="github" name="texane/stlink" path="toolchain/stlink"/>
 11
 12     <!-- toolchain -->
 13     <project remote="crosstool-ng" name="crosstool-ng" path="toolchain/crosstool-ng"/>
 14     <project remote="frosted" name="elf2flt" path="toolchain/elf2flt"/>
 15     <project remote="frosted" name="newlib" path="toolchain/newlib" revision="frosted">
 16         <linkfile src="../../.repo/manifests/ctng-custom-elf2flt.patch" dest="toolchain/ctng-custom-elf2flt.patch"/>
 17         <linkfile src="../../.repo/manifests/arm-frosted-eabi.config.in" dest="toolchain/arm-frosted-eabi.config.in"/>
 18         <linkfile src="../../.repo/manifests/buildtoolchain.sh" dest="buildtoolchain.sh"/>
 19     </project>
 20
 21     <!-- kernel + userspace -->
 22     <project remote="frosted" name="frosted" path="frosted"/>
 23     <project remote="frosted" name="libopencm3.git" path="frosted/kernel/libopencm3"/>
 24     <project remote="frosted" name="busybox.git" path="frosted/apps/busybox"/>
 25     <project remote="frosted" name="picotcp" path="frosted/kernel/net/picotcp"/>
 26     <project remote="frosted" name="frosted-userland.git" path="frosted/frosted-userland"/>
 27
 28 </manifest>
I want to replace the repositories described at lines 22 and 26 with my own repositories. I start off by going to github, finding those repositories, and clicking on the Fork button in the web interface for both. Then I create my .repo/local_manifests/roomservice.xml file with the following contents:
  1 <?xml version="1.0" encoding="UTF-8"?>
  2 <manifest>
  3         <remote fetch="ssh://git@github.com/twoerner/" name="origin"/>
  4         <remove-project name="frosted"/>
  5         <remove-project name="frosted-userland.git"/>
  6         <project remote="origin" name="frosted.git" path="frosted" revision="contrib/twoerner-master"/>
  7         <project remote="origin" name="frosted-userland.git" path="frosted/frosted-userland" revision="contrib/twoerner-master"/>
  8 </manifest>
 At this point I simply invoke "repo sync" (you might need to add --force-sync) and you're all set! Those repositories will now be sync'ed from your github copies, you can work in the code of those repositories, make commits, and push them up to github.

Notice that the names that are used in the <remove-project.../> lines are the same names as the lines from the original manifest that I want to replace.

Did you notice that I used "origin" as the remote name? When repo clones this repository, it will use this name as git's remote name, and since git assumes the primary remote's name is "origin", this configuration simply makes life a touch easier. You're free to use whatever remote name you want, but in this case you'll just need to run add your remote's name the first time you "git push..." .


[1]
"What is repo?" repo is a tool created by (and very popular with) Android developers to manage building software comprised of sets of git repositories. Many software projects fit into one git repository, but sometimes a project likes to keep separate git repositories for different parts of the project. This, then, creates a burden on the developer to make sure the correct repositories, are cloned to the right places, and checked out at the right commits. repo is a tool that lists which repositories are used, where to place them relative to one starting directory, and checks out a specific revision/commit. Therefore it removes the extra burdens caused by multi-repository projects. repo also has functionality to allow your project to integrate with gerrit (a code review system), but that's another topic. For more information on repo try:

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