Using Git submodules to share modified Drupal modules across sites

This reference is currently somewhat specific to Agaric's setup. We currently use Drush to update modules rapidly on a per-site basis (rather than updating a module in a central location and pushing it to the sites that use it), but certain modules have special needs (extra files, a patch that needs to be applied and hasn't been committed to Drupal.org version control yet) and when these modules have to be used on multiple sites, we can save time by bringing them in as submodules. Here are the notes from the first time we did this.

On submoduling, we need our copy of special module to include the excellent modification patch, so I have that working locally for superb client but not committed. I need to commit it somewhere and make it a submodule for both superb client site one and superb client site two

Reading the submodule documentation made me significantly less sure of what i should be doing

Stefan Freudenberg to the rescue.

(Last step first, to add a repo as a submodule it's git submodule add <repo> <workdir path>.)

First step is creating the repo. Should I take the files out of the repo they are in before doing anything with them? (creating the submodule repo), I ask, but Stefan says that is not necessary. You can start a subproject by running git init in a workdir subdirectory.

The special module is committed to superb client site one but the excellent modification patch, a Drupal "sub"module, is not, but it is physically in my local superb client one working copy.

For regular use (bringing the module into new projects) scroll down to "Pulling a shared module into your site project."

Adding a module for centralized distribution

So still first, create a repository for special module: run git init in the special module directory, within the project. It's possible.

cd /path/to/drupal/sites/all/modules/special_module
git init

Initialized empty Git repository in /path/to/drupal/sites/all/modules/special_module/.git/

Also create a repo on the server, just initialize a bare repository where you can push:

mkdir /srv/git/drupal-modules/specialmodule.git
cd /srv/git/drupal-modules/specialmodule.git
git init --bare

After doing so

git remote add origin git.agariclabs.com:/srv/git/drupal-modules/special_module.git

Try to push. Here we failed a couple times with a wrong path and then still no refs in common until using push origin master.

git commit first
we have initiliazed but not added content ot the repo.
don't forget to git add .

try to git fetch
the remote end hung up unexpectedly
and what is the error message?
that is it
preceded by "fatal:"

Can you try to push again, please.
git push origin master
from your special module directory
if that does not work run git branch
to see what branch you are in

failed also. the git remote add origin path must be wrong?

• master

git.agariclabs.com:/srv/git/drupal-modules/special_module.git

git push origin master worked

now you can try to make it a submodule
got to yourcontaining workdir root
and try git submodule add git.agariclabs.com:/srv/git/drupal-modules/special_module.git
such as drupal/sites/all/modules/special_module

git submodule add git.agariclabs.com:/srv/git/drupal-modules/salesforce.git drupal/sites/default/modules/salesforce
"Adding existing repo"

now check in special_module if you are still on a branch

in your superproject run git submodule status
does the hash value have a plus or minus sign?

... a minus

then run git submodule init
from the main project root

registered path

and now it has no sign
perfect.
it will show a plus if it's not in sync

now enter the special_module directory and run git branch

• master

good so you can still work there. if you check out a new submodule it will have no branch.
you can try to add that submodule in another project now.

Pulling a shared module into your site project

Maybe it will work for you.

cd /var/www/theproject
git submodule add git.agariclabs.com:/srv/git/drupal-modules/special_module.git drupal/sites/default/modules/special_module
git submodule status
git submodule init
git submodule update
cd drupal/sites/default/modules/special_module
git checkout master
cd --
git status
git add .gitmodules
git add drupal/sites/default/modules/special_module/
git commit -m "Installed centrally maintained version of special_module as a submodule."
git push

Resolution