gh-pages branch fails to build at GitHub but runs flawlessly locally

Question

I have two sub-modules in the gh-pages branch of particular project. Every time I push this project I receive this familiar message in my mail box:

The page build failed with the following error:

The submodule registered for ./updates/4.4.luna could not be cloned. Make sure it's using https:// and that it's a public repo. For more information, see https://help.github.com/articles/page-build-failed-invalid-submodule .

This only refers to one of the sub-modules, even though both are configured the same way. They are both public and registered with https:// addresses in the local repository:

$ git submodule foreach -q git config remote.origin.url
https://github.com/ldesousa/dsl3s.update.4.3.kepler.git
https://github.com/ldesousa/dsl3s.update.4.4.luna.git

I went through the trouble of installing Jekyll to run the site locally (boy, the instructions at the GitHub page are poor). And locally everything runs perfectly; Jeckyll reports no errors at all.

What else can I do to solve this? Or at least to understand why the repository is failing to build at GitHub?

Answer 1

Ok, after some more digging I found out that the metadata in the main repository was not coinciding with that of of the sub-modules:

$ cat .gitmodules
[submodule "updates/4.3.kepler"]
    path = updates/4.3.kepler
    url = https://github.com/ldesousa/dsl3s.update.4.3.kepler.git
[submodule "updates/4.4.luna"]
    path = updates/4.4.luna
    url = git@github.com:ldesousa/dsl3s.update.4.4.luna.git

So I had to correct the last URL for the http:// version and then run:

git submodule sync