A git microtutorial by example

git_short_tutorial-en.sh

# start creating a new Rails application
rails silly_blog
cd silly_blog

# put it under version control with Git
git init
git add .
git commit -a -m "first commit"

# we are in "master" branch
git branch

# do some modifications (eg: add a new model)
ruby script/generate model Post title:string body:text
git add .
git commit -a -m "added post model"

# the log reflects alle the commits
git log

## Add an "experimental" feature

# make a new branch
git branch experimental
git checkout experimental
ruby script/generate model Rating value:integer post:references
git add .
git commit -a -m "added rating model"
git checkout master

# we are happy with these modifications, put them under the "master" branch
git merge experimental

# modify the "experimental" branch, without commit them
git checkout experimental
# modify the Rating model
cat "class Rating < ActiveRecord::Base; belongs_to :post; end" > app/models/rating.rb
git checkout master
git status
# moficiation tainted the "master" branch too

# go back into "experimental" branch and do a commit
git checkout experimental
git commit -a -m "now ratings belong to posts"
git checkout master
git status
grep "belongs_to" app/models/rating.rb
# modifications stay in "experimental" branch,
# to import it:
git merge experimental

## Conflicts management

# let's add a new file (TODO) into "master" branch
echo "#List of next actions to accomplish" > TODO
git add .
git commit -a -m "added a (empty) list of next actions"

git checkout experimental
# notice that the TODO file doesn't exists here
# let's import the most recent modifications
git pull . master

# let's add an action (in "experimental" branch)
echo "* write unit tests" >> TODO
git commit -a -m "added some action" 

# let's add an action (in "master" branch)
git checkout master
echo "* buy milk" >> TODO
git commit -a -m "remember the milk"

# now the two version of TODO are in "conflict"
git checkout experimental
git pull . master
# during merging a conflict happens!

echo "# List of next actions to accomplish"	 > TODO
echo ""						>> TODO
echo "* write unit test"			>> TODO
echo "* buy milk"				>> TODO
git commit -a -m "resolved conflicts on next things to accomplish"

git checkout master
git merge experimental
# now everything is aligned

## Let's housekeeping
cd ..
rm -fr silly_blog