Git/Submodules

Notes

I use submodules to organize groups of related repositories and make checking out lots of repos a breeze.

Adding Submodules to Repository

Check out the repository that you want to put submodules into:

git clone https://charlesreid1.com:3000/rpi/pi-master.git
cd pi-master

Now add submodules:

git submodule add <git-repo-url>

Here's the script:

#!/bin/bash

git submodule add https://charlesreid1.com:3000/rpi/pi-opencv.git
git submodule add https://charlesreid1.com:3000/rpi/pi-startup-services.git
git submodule add https://charlesreid1.com:3000/rpi/pi-transmission.git
git submodule add https://charlesreid1.com:3000/rpi/pi-stunnel.git
git submodule add https://charlesreid1.com:3000/rpi/pi-setup.git
git submodule add https://charlesreid1.com:3000/rpi/pi-process-wifi-data.git
git submodule add https://charlesreid1.com:3000/rpi/pi-join-wifi.git
git submodule add https://charlesreid1.com:3000/rpi/pi-aircrack-batch.git

This will add a .gitmodules file automatically.

When you're done, make the commit:

git commit -am 'adding submodules'

Checking Out Repository with Submodules

Start by checking out the repository with the submodules:

git clone https://charlesreid1.com:3000/rpi/pi-master.git

Initialize the repository submodules:

git submodule init

or, do it all at once:

git clone --recursive https://charlesreid1.com:3000/rpi/pi-master.git

or,

git clone --recurse-submodules https://charlesreid1.com:3000/rpi/pi-master.git

https://stackoverflow.com/questions/3796927/how-to-git-clone-including-submodules#4438292

Checking Out Submodules in Existing Repository

If you already have a repository cloned and you just don't have the submodule contents (git won't check out submodule contents by default), you can initialize the contents of the submodules by running:

git submodule update --init 

or, if there are multiple folders,

git submodule update --init --recursive

Fetching Changes to Submodules

To pull changes for each of the submodules, run

git submodule update --remote

Dealing with Detached Heads

For whatever reason, git submodules will not automatically take master with them when you make commits directly inside of the submodule directory. So, annoyingly, you run into a problem with commits that you made being on a detached head.

For example, suppose you are doing work on the master branch (commit e1de9), and then you're ready to commit your changes. So you do, resulting in commit a067c89. But git says that commit is a detached head.

Here's what the log looks like:

$ git log --all
commit a067c89c6f3d853f42c28e37143978c24c0542f3 (HEAD)
Author: Charles Reid <charlesreid1@gmail.com>
Date:   Mon Mar 12 05:09:43 2018 -0700

    moving config files into their own directories, one for each program

commit e1de9742b2d669fe74942eb3977b81fb9cd73619 (origin/master, origin/HEAD, master)
Author: Charles Reid <charlesreid1@gmail.com>
Date:   Mon Mar 12 08:14:11 2018 +0000

    put local settings in debug mode.

commit f2202c34e51b2c5be3b48e0f070fcd100864a86e
Author: Charles Reid <charlesreid1@gmail.com>
Date:   Mon Mar 12 01:37:39 2018 +0000

    added LocalSettings.php. Fixing show exceptions value.

How to resolve this hairy situation?

The solution is to turn the head-less commit that you just made into a branch, and then merge that branch into master.

Start by turning the headless commit into a branch:

$ git branch <new-branch-name> a067c89

in this case, I ran:

<pre>
$ git branch stuff a067c89
<pre>

Now we have created a branch stuff with our new changes.

To get these changes into master, we just merge the two branches stuff and master:

<pre>
$ git merge master stuff
Updating e1de974..a067c89
Fast-forward

and a git push finishes it off:

$ git push
Counting objects: 5, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (4/4), done.
Writing objects: 100% (5/5), 1.41 KiB | 1.41 MiB/s, done.
Total 5 (delta 0), reused 0 (delta 0)
To https://charlesreid1.com:3000/wiki/charlesreid1-config.git
   e1de974..a067c89  master -> master

WTF Git Why Do You Keep Detaching Heads

I can't figure out why I'm suddenly having this problem.

Git keeps detaching heads. Particularly, when you do a git clone --recursive.

As of 2013, git 1.8, we should be able to track branches, and yet I'm sitting here like a damn caveman trying to update each individual submodule for each individual commit, so that 1 commit turns into 5.

Resources

https://git-scm.com/book/en/v2/Git-Tools-Submodules