subtree-training-main

Git subtree training (main repo)

In this repository, I'll show you how to use git subtree in hands-on style.

You'll fork the repository and reference the sub repository as a subtree inside the forked repository.

0. Fork this repository and clone it in your wokring dir.

• Click fork button.

• Clone your fork in your local PC.

git clone {your-fork-repository-url}
cd subtree-training-main

(From now on, all operations are done in subtree-training-main directory.)

1. Add subtree.

Add subtree-training-sub repository as subtree in ./sub directory using --prefix option.

# Make a feature branch
$ git checkout -b subtree-training
$ git subtree add --prefix sub [email protected]:satoshikumano/subtree-training-sub.git master --squash

You can confirm sub/README.md is added in the main repository. And there's new commits in the main repository made by subtree command.

$ git log
commit e902fbdab9827809666a4499a15454c2828a5414 (HEAD -> sample)
Merge: fef3203 f86ad4d
Author: satoshi <[email protected]>
Date:   Thu Sep 7 15:15:40 2017 +0900

    Merge commit 'f86ad4db4dfac8804b54f030006a87659e8ff922' as 'sub'

commit f86ad4db4dfac8804b54f030006a87659e8ff922
Author: satoshi <[email protected]>
Date:   Thu Sep 7 15:15:40 2017 +0900

    Squashed 'sub/' content from commit 8b63f9a
    
    git-subtree-dir: sub
    git-subtree-split: 8b63f9a11dd3713e260d8300035773158a6c8906

2. Fetch updates in sub repository.

Assume branch1 branch in the sub repository is pushed and you want to pull the changes in the branch to the main repository.

(Note that in real project you'll probably update the reference commit on master or develop branch. Using branch1 here is just to simplify the flow and focus on key concepts in subtree.)

• Add remote to shoten the command line inputs.

$ git remote add sub-origin [email protected]:satoshikumano/subtree-training-sub.git

• Pull the changes in the sub repository

$ git pull -s subtree sub-origin branch1 --allow-unrelated-histories --squash
From github.com:satoshikumano/subtree-training-sub
 * branch            branch1    -> FETCH_HEAD
Auto-merging sub/README.md
CONFLICT (add/add): Merge conflict in sub/README.md
Squash commit -- not updating HEAD

Since specified --squash option, it causes conflict. To deal with the situation,

Edit sub/README.md and resolve conflict

$ git add sub/README.md
$ git commit

Alternatively, you can omit --squash option. In this case, all historiy objects in the subrepository are copied to the main repo.

[WIP] Using git subtree pull to pull the changes in the sub repository.

It doesn't works well.

Pull the changes in the sub repository with --squash option

$ git subtree pull --prefix ./sub sub-origin branch1 --squash
warning: no common commits
remote: Counting objects: 6, done.
remote: Compressing objects: 100% (4/4), done.
remote: Total 6 (delta 1), reused 3 (delta 0), pack-reused 0
Unpacking objects: 100% (6/6), done.
From github.com:satoshikumano/subtree-training-sub
 * branch            branch1    -> FETCH_HEAD
 * [new branch]      branch1    -> sub-origin/branch1
Can't squash-merge: './sub' was never added.

Pull the changes in the sub repository without --squash option

$ git subtree pull --prefix ./sub sub-origin branch1 --squash
From github.com:satoshikumano/subtree-training-sub
 * branch            branch1    -> FETCH_HEAD
fatal: refusing to merge unrelated histories

It seems git has an issue dealing with it.

I'm using git version 2.14.1 installed by homebrew. It would not happens in later or older version.

3. Push changes to the main repository

After you have updated the sub repository reference, push the working branch and make a PR to master or deveplop branch So that you team member can use the main repository code with the latest sub repository references.

$ git push origin subtree-training

And make a PR in github with the branch!