Advanced git concepts

The not-so-every day workflow

Please fork the repo in your own account before attempting the tutorial

Merging

Scenario 1: You need to add a new category of films, but that is not due to be released yet. Your team has decided that the work is going to be done on a branch, until the feature is ready to be released

Checkout a new brach called scifi

  git checkout -b scifi

Create a folder called scifi inside the movies folder
Create a file blade_runner.txt in the scifi folder, using your favourite text editor
Make changes to the file and commit them

  git add .
  git commit -m "Add Blade Runner to scifi films"

Push the branch to the remote repository

  git push -u origin scifi:scifi

Let's have a look at the git log

  git log --oneline --decorate --graph

The feature is nearly done, but there is some urgent work that needs to be done on master and you need to push a hotfix

Checkout master
Add movies/film_noir/the_maltese_falcon.txt
Push the change to master

  git checkout master
  git add .
  git commit -m "Message"
  git pull
  git push
  git log --pretty=oneline --decorate

Let's finish the feature and merge it back to master

checkout the scifi branch

  git checkout scifi

Make a change in the blade_runner.txt file and push it to the remote

  git add .
  git commit -m "Short meaningful message"
  git push

Merging

  git checkout master
  git merge scifi
  git log --oneline --decorate --graph
  git push

Rebasing

Scenario 2: You are doing some experimental work locally, that is not yet ready to be pushed. You are working on a branch, in order to semantically differentiate it from the master

Create a branch called thriller
Add thriller/spectre.txt to the branch
Don't push the changes yet!

  git checkout -b thriller
  git add .
  git commit -m "Add Spectre to thriller films"
  git log --pretty=oneline --decorate

The experimental work is nearly done, but there is some urgent work that needs to be done on master and you need to push a hotfix

Checkout master
Make a change to film_noir/maltese_falcon.txt
Push to the remote

  git checkout master
  git add .
  git pull
  git push
  git log --pretty=oneline --decorate

Let's finish the experimental work and merge it back to master

Edit the spectre.txt file and make another change
Commit the change
Rebase the thriller branch onto master

  git checkout thriller  
  <edit spectre.txt>
  git add .
  git commit -m "Message"
  git rebase master
  git log --pretty=oneline --decorate --all --graph

Switch back to master
Merge the thriller branch

  git checkout master
  git merge thriller
  git log --pretty=oneline --decorate --all --graph

Interactive rebase

Scenario 3: You want to open source your movie data, but your commit history contains a lot information that should not be available to the wide world, so we need to clean all that up before releasing it

Create a branch called open-sourcing
Create a directory called animation inside movies
Add, commit movies/animation/my_neighbour_totoro.txt
Add, commit movies/animation/the_cat_returns.txt
Add, commit movies/animation/princess_mononoke.txt && animation/kikis_delivery_service.txt
Make a change to movies/animation/the_cat_returns and commit

Don't push the changes to the remote yet

Run interactive rebasing (before the commits have been pushed)

  git rebase -i HEAD~4

This will open up a text editor with the latest 4 commits

Edit one of the commits (to split it in two)

  git reset HEAD~1
  git add movies/animation/princess_mononoke.txt
  git commit -m "Add Princess Mononoke"
  git add movies/animation/kikis_delivery_service.txt
  git commit -m "Add Kiki's delivery service"
  git rebase --continue

Reorder commits
Squash commits

Conflicting changes

Scenario 4: You are making some important changes to the Scifi section that are not yet ready to be released. At the same time, you need to maintain the Scifi code that is already on master (conflicting changes)

Checkout the scifi branch
This branch is behind master, as some work has been done on master since the last time we merged the branch
Merge the master into the scifi branch

  git checkout scifi
  git merge master
  git status
  git push

Make some changes to movies/scifi/blade_runner.txt file on the scifi branch

  git add .
  git commit -m "Meaningful message"
  git push

Checkout master
Make some other changes to the movies/scifi/blade_runner.txt file
Commit the changes but don't push them yet

  git checkout master
  <make some other changes to blade_runner.txt>
  git add .
  git commit -m "Message"

The branch is ready to be merged into master

  git merge scifi

We now have to resolve the conflicts

Choose the version on the branch, using your favourite text editor

  git add .
  git commit

Other useful commands

git cherry-pick
git reflog git updates reflog every time HEAD moves (can resurrect branches and lost work)

Useful resources

http://git-scm.com/book/
https://www.atlassian.com/git/tutorials/