The original repository contains "submodules", which Yocto / bitbake support. The original repository also uses autotools, which Yocto / bitbake also support. The problem appears when trying to use both things at the same time: the existing Yocto / bitbake support does not have the concept of configure scripts in multiple subdirectories. The way autotools supports this is by having a statement like this:
AC_CONFIG_SUBDIRS([submodules/bm])
in the toplevel configure.ac. This is the reason why this repository
added that file, to be able to drive the configure process of the
submodules.
Since trying to manage the submodules proved to be a pain in the context of Yocto, the git submodules were replaced with git subtrees, which creates a single repository with the contents of the submodules added to it. In order to recreate the repository, do this:
$ git remote add -f behavioral-model https://github.com/p4lang/behavioral-model.git
$ git subtree add --prefix submodules/bm behavioral-model master --squash
$ git remote add -f submodules/p4c-bm https://github.com/p4lang/p4c-bm.git
$ git subtree add --prefix submodules/p4c-bm p4c-bm master --squash
If you need to update a subtree, do this:
$ git subtree pull --prefix submodules/bm behavioral-model master --squash
Instead of master, you can use any valid reference (commit, branch, tag). Just keep in mind that it refers to the remote you are specifying and not to local references.
Strictly speaking it's not necessary to add the remotes and you can use the URL in place of the remote name in the corresponding 'git subtree add' line.
git subtree is mostly syntax sugar for adding git trees at specific
graft points. This blog post from
Atlassian
contains a nice summary.