clone submodules for go_modules file fetcher

[aminjam]

We have a go_modules project that utilizes submodules and we use replace directives from the main modules to access other modules. When we run dependabot we see errors that couldn't read go.mod from the submodule.

updater | ERROR <job_206648398> go: code.cloudfoundry.org/[email protected] (replaced by ../garden): reading ../garden/go.mod: open /home/dependabot/dependabot-updater/repo/src/garden/go.mod: no such file or directory

I was able to fix this issue locally and successfully run ./bin/dry-run.rb after changing this line to be the following:

git clone --no-tags --recursive #{br_opt} #{source.url} #{path}

Is it possible to solve this issue in a different way? If not, would it be possible to add a new config so that repositories can clone submodules for go_modules projects?

[jakecoffman]

Submodule cloning was added in #5982 so this should be working now!

Let us know if you're seeing any issues with it.