Git Subrepo Command

It's natural to want to use other projects as dependencies of your project.
Without git subrepos there are several ways to do this:

Require the user to build the dependency manually
- Somewhat silly for header-only or other non-compiled dependencies
- Increases effort to use your project
- Can be annoying for users due to version incompatibilities
Copy/paste, put a tar-ball, etc. of the dependencies source code inside your project.
- This is probably the worst option because:
  - Loose version control of dependency.
  - Git history stores entire source (bundle several versions of Boost with your repo and watch your clone's start taking forever).
Assuming your project is under CMake, add the dependency as external_project
- Again silly of header-only or other non-compiled dependency
- Requires an internet connection to build (source downloaded at build time)
Use git submodules
- "Canonical" git solution
- Pain to use
  - Need to remember to always clone with --recursive
    - Forgetting to do this means needing to run git submodule update --init --recursive for each submodule
  - Updating submodule is error-prone
    - Requires changes in two git repos (the parent repo and the dependency)
    - Easy to get into a messed-up history
Use git subtrees
- No enforced distinction between repos
- Merging becomes complicated

Git subrepo homepage attempts to provide a better solution than either submodules or subtrees.

Using Git Subrepo

The documentation of the subrepo command is quite good. The quick and dirty of it is:

Add a subrepo to your project:

#In root of your project
git subrepo clone <repo to add>

Update a subrepo:

#In root of your project
git subrepo pull <directory containing subrepo>

Contribute back to the subrepo's project:

#In root of your project
git subrepo push <directory containing subrepo>

Users of your project do not need subrepo command to use your repo
Commits to a subrepo are part of the parent repo's history, unless you explicitly push them back to the subrepo.