[Git] Submodule

SUBMODULE

You're in the process of putting together two websites. One is for the Mythical Wildlife Fund: MWF.com. The other site is an adoption site for stray unicorns called unicornrescues.com. Both sites will share code for a JavaScript image gallery along with the associated css. Let's get started by adding a submodule containing the JavaScript at"git@petstore.com:gallery_js.git".

$ git submodule add "git@petstore.com:gallery_js.git"
 

Cloning into 'gallery_js'...
done.

 

STAGING A SUBMODULE

All that's left to do is to commit your submodule so that other collaborators can use it. Using a single git command, stage the current changes to .gitmodules and gallery_js.

$ git add --all

 

COMMITTING A SUBMODULE

Great! Now go ahead and commit the submodule. Don't forget the commit message!

$ git commit -m "Add gallery_js submodule"
 

[master 4adec83] Add gallery_js submodule
 2 files changed, 4 insertions(+)
 create mode 100644 .gitmodules
 create mode 160000 gallery_js

 

INIT SUBMODULE

You're helping a co worker get set up to work on unicornrescues.com. You've already cloned the repo. Next, initialize the submodules so they download their own contents.

$ git submodule init
 

Submodule 'gallery_css' (git@petstore.com:gallery_css.git) registered for path 'gallery_css'
Submodule 'gallery_js' (git@petstore.com:gallery_js.git) registered for path 'gallery_js'

Success!

 

UPDATE SUBMODULES

Now that you have the submodules initialized, you need to check for updates and make sure they have the correct commits checked out. Run the submodule command that does this.

$ git submodule update
 

Cloning into 'gallery_css'...
done.
Submodule path 'gallery_css': checked out 'f509481d3935300afd1aaec7a79455a47cc0abba'
Cloning into 'gallery_js'...
done.
Submodule path 'gallery_js': checked out '9f29d1dd5068ed755f6a9a89338e2557ed7c810f'

Success!

 

DETACHED HEAD

You've just committed a few changes to the gallery_css submodule. When you go to push, you realize that you're in a detached head state. Don't panic, though! We can fix it. Let's start out by creating a new branch with your most recent commit: "a7eded4". Name the branchtemp_changes.

$ git branch temp_changes "a7eded4"

 

BRANCH MERGE

Your seemingly lost changes now reside on the temp_changes branch. Go ahead and merge the temp_changes branch back into master.

$ git merge temp_changes
 

Updating f509481..9043206
Fast-forward
 gallery.css |    2 ++
 unicorn.rb  |   13 +++++++++++++
 2 files changed, 15 insertions(+)
 create mode 100644 unicorn.rb

Success!

 

PUSH CHECK

After finishing up a bunch of changes, you want to push them up to the remote so you can share it with your other co-workers that are working on the project. Since you're using submodules, you should make sure to use the option which checks whether you have un-pushed submodules.

$ git push --recurse-submodules=check
 

Counting objects: 3, done.
Delta compression using up to 2 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (2/2), 308 bytes, done.
Total 2 (delta 0), reused 0 (delta 0)

Success!

 

ON DEMAND PUSH

We need to push submodule changes again. But this time, instead of going into the submodule to push it, just use the on-demand option for the --recurse-submodules option. This way submodules that need it will be pushed automatically.

$ git push --recurse-submodules=on-demand
 

Counting objects: 3, done.
Delta compression using up to 2 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (2/2), 308 bytes, done.
Total 2 (delta 0), reused 0 (delta 0)

Success!

 

ON DEMAND ALIAS

Wouldn't it be nice if you didn't have to type that long line out every time you wanted to push this project? Let's make the command easier to use. Create an alias which will run the git push --recurse-submodules=on-demand command. Name the alias anything you want.

$ git config alias.pushall "push --recurse-submodules=on-demand"