Checking out submodules should take advantage of .git/modules

[jspahrsummers]

carthage checkout --use-submodules can be really slow for some cases of recursive submodules. It's exacerbated because we don't reuse existing clones that exist within .git/modules/ of the parent repository.

When a repository already exists in .git/modules/, we should probably try reusing it before cloning from Carthage's private cache.

[robrix]

Sounds like a really good idea 👍

[jspahrsummers]

The even-simpler solution might be to just bypass Carthage's cache for the --use-submodules case. That might be acceptable.

[c0diq]

My project needs to compile for a lot of different platforms and include a dependency as a submodule currently. I would like Carthage to use the that submodule (and path) when building for iOS or OSX however when I pass --use-submodules Carthage adds a new entry to my submodule to Carthage/Checkouts/XXX. Is or will there be a way for Carthage to use an existing submodule location?

[robrix]

Currently, Carthage expects its dependencies to live in Carthage/Checkouts, and there is not currently any way to tell it not to. I’d suggest using a new issue if that’s valuable to you—this issue is about handling the repo, whereas the checkouts are the working directory.