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denis-ryzhkov / git-intro

Tech demo about Git.

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GIT Intro

Abstract

From http://en.wikipedia.org/wiki/Git_(software)

  • Git is a distributed revision control and source code management (SCM) system with an emphasis on speed.
  • Git was initially designed and developed by Linus Torvalds for Linux kernel development in 2005.
  • Based on a recent survey of Eclipse IDE users, Git is reported to have 30% adoption as of 2013.
  • Every Git working directory is a full-fledged repository with complete history and full version tracking capabilities, not dependent on network access or a central server.
  • Strong support for non-linear development
  • Distributed development
  • Compatibility with existing systems/protocols
  • Efficient handling of large projects
  • Cryptographic authentication of history
  • Toolkit-based design
  • Pluggable merge strategies
  • Garbage accumulates unless collected
  • Periodic explicit object packing

Git vs SVN

From https://git.wiki.kernel.org/index.php/GitSvnComparison

  • Git is much faster than Subversion
  • Subversion allows you to check out just a subtree of a repository; Git requires you to clone the entire repository (including history) and create a working copy that mirrors at least a subset of the items under version control.
  • Git's repositories are much smaller than Subversions (for the Mozilla project, 30x smaller)
  • Git was designed to be fully distributed from the start, allowing each developer to have full local control
  • Git branches are simpler and less resource heavy than Subversion's
  • Git branches carry their entire history
  • Merging in Git does not require you to remember the revision you merged from (this benefit was obviated with the release of Subversion 1.5)
  • Git provides better auditing of branch and merge events
  • Git's repo file formats are simple, so repair is easy and corruption is rare.
  • Backing up Subversion repositories centrally is potentially simpler - since you can choose to distributed folders within a repo in git
  • Git repository clones act as full repository backups
  • Subversion's UI is more mature than Git's
  • Walking through versions is simpler in Subversion because it uses sequential revision numbers (1,2,3,..); Git uses unpredictable SHA-1 hashes. Walking backwards in Git is easy using the "^" syntax, but there is no easy way to walk forward.

Explain key concepts

  • Working copy.
  • Index aka Stage.
  • Commit.
  • Remote.

Introduce yourself

git config --global user.name "Name Surname"
git config --global user.email "your@email.com"
cat ~/.ssh/id_rsa.pub
# ssh-rsa AAAAB3Nza...HL7a0lz denisr@denisr.com
# ssh-keygen

Clone repo

git clone git@github.com:denis-ryzhkov/git-intro.git
cd git-intro

Create repo

mkdir git-intro && cd $_
git init
echo '*.pyc' > .gitignore
git add .gitignore
git commit -am 'See #1: Initial commit with ".gitignore" only.'
git remote add origin git@github.com:denis-ryzhkov/git-intro.git
git push -u origin master

Update code from local to remote

echo 'Hello world' > index.html
echo '*.log' >> .gitignore
git add index.html
git status
# git checkout -- file
git diff
git diff --color-words
git diff --staged
git commit -am 'See #1: Prototype of Facebook v42.'
git push

If repo has branches:

git push origin master

Implicit "git push" behavior is git-config and git-version specific,
so unreliable: http://stackoverflow.com/a/9749535/350937

Update code from remote to local

git pull

git stash
git pull
git stash pop

git commit -am 'WIP'
git pull
git commit -am 'Finished: ...'

Aliases

git config alias.l "log --decorate=full --graph --color=auto --all"
git l

~/.alias:
alias gl='git log --decorate=full --graph --color=auto'
alias gla='gl --all'
alias gs='git status'
alias gsu='git submodule update'
alias gcr='git log --reverse -p --full-diff' # be4b4f4..HEAD # code review

~/.profile:
source $HOME/.alias

Branches

Create:

git checkout master && git pull
git checkout -b feature
git push -u origin feature

Update:

git checkout master && git pull
git checkout feature
git merge --no-ff master

Merge:

git checkout master
git merge --no-ff feature
# Fix conflicts.
git add fixed1 fixed2 fixedN
git commit
# OR
git merge --abort

Delete:

git checkout master
git branch -d feature
git push origin :feature

Rebase

gl
git rebase -i e4b6e03ff91384df2bc7e09737b6f3a26a362c61
# pick, reword, squash, etc.
# OR
git rebase e4b6e03ff91384df2bc7e09737b6f3a26a362c61
# Fix conflicts.
git rebase --continue
# OR
git rebase --abort
git push -f origin feature
# Re bad practice.

Revert

git revert e4b6e03ff91384df2bc7e09737b6f3a26a362c61

Reverting merges:

# Let M is merge commit.
git revert M
# Produces RM
# Later:
git revert RM
# Explain why.

Amend, Checkout, Reset

git commit --amend -am 'Old code. And new code too.'

git checkout e4b6e03ff91384df2bc7e09737b6f3a26a362c61
git checkout master

git reset --soft e4b6e03ff91384df2bc7e09737b6f3a26a362c61
# Fix.
git commit -am 'Fixed...'

git reset --hard e4b6e03ff91384df2bc7e09737b6f3a26a362c61
git push -f origin feature

Patch, Cherry-Pick

git diff > patch.diff
git apply patch.diff

git cherry-pick e4b6e03ff91384df2bc7e09737b6f3a26a362c61

Tags

git tag v42
git push origin v42

GitFlow

http://nvie.com/posts/a-successful-git-branching-model/

About

git-intro version 0.1.2
https://github.com/denis-ryzhkov/git-intro
Copyright (C) 2013 by Denis Ryzhkov denisr@denisr.com
MIT License, see http://opensource.org/licenses/MIT

About

Tech demo about Git.