Git
Git
By Julien Muetton / @themouette
Setup
Download an install
Refer to online documentation
git help
To get some help on a command.
$ man git-commit $ git help $ git help commit
Git Book is a golden mine too.
Generate an ssh key
$ cd ~ $ ssh-keygen -t rsa $ cat id_rsa.pub ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAyyA8wePstPC69PeuHFtOwyTecByonsHFAjHbVnZ+h0dpomvLZxUtbknNj3+ c7MPYKqKBOx9gUKV/diR/mIDqsb405MlrI1kmNR9zbFGYAAwIH/Gxt0Lv5ffwaqsz7cECHBbMojQGEz3IH3twEvDfF6cu5p 00QfP0MSmEi/eB+W+h30NGdqLJCziLDlp409jAfXbQm/4Yx7apLvEmkaYSrb5f/pfvYv1FEV1tS8/J7DgdHUAWo6gyGUUSZ JgsyHcuJT7v9Tf0xwiFWOWL9WsWXa9fCKqTeYnYJhHlqfinZRnT/+jkz0OZ7YmXo6j4Hyms3RCOqenIX1W6gnIn+eQIkw== my computer
Then add the public key content to github, bitbucket, gitlab or any other server and test everything is all right.
$ ssh git@github.com Hi themouette! You've successfully authenticated, but GitHub does not provide shell access.
Configure your identity
$ git config --global user.name "John Doe" $ git config --global user.email johndoe@example.com
Configure your editor
Default is vi, but if you really want to change:
$ git config --global core.editor emacs
$ git config --global core.editor \
"'C:/Program Files/Notepad++/notepad++.exe' \
-multiInst -notabbar -nosession -noPlugin"
Configure your diff tool
$ git config --global merge.tool vimdiff
Add some alias
Version Control
A bit of theory
Definition
Version control is a system that records changes to a file or set of files over time so that you can recall specific versions later.
Local
Local version system put in the same place versions and working directory.Centralised
In centralized version control everything is tracked on the server, clients just check out the latest snapshot of the files.Decentralized
In decentralized version control, every client mirror the whole repository.GIT is decentralized
Getting Started
Local first
Everything is local, remote operations are only for sharing.
git init
Create an empty git repository or reinitialize an existing one.
$ git init Initialized empty Git repository in ~/.git/
Running git init in an existing repository will not overwrite things that are already there.
Commit
A commit is a snapshot of your working tree and a pointer to previous commit.
Three Zones
Everything in GIT is in one of those following area.
- Working directory: the directory you work in;
- Staging area: prepare next commit;
- Repository: history of every committed change.
Three Zones
Local Repository
git add file
Add file contents to the staging area.
$ git add README
Track a file for the first time.
Track changes on file since previous commit.
git checkout [file]
Checkout a branch or paths to the working tree.
$ git checkout README $ git checkout my-branch
Reset file/path to staging area's version.
Switch branch.
git commit
Create a commit from current staging area's status.
$ git commit [master 8a6e1a3] My awesome message.D 2 files changed, 10 insertions(+), 4 deletions(-) create mode 100644 img/01/branch.png
Returns the commit hash 8a6e1a3.
To edit your latest commit, use git commit --amend.
git status
Show current working dirrectory and staging area.
git mv src destination
Rename src into destination.
git rm file
Delete file from tracking.
git log [file]
Show commit logs.
$ git log
commit 8fbdc87e2f254c1c52ee9c2cae886985421fd3ef
Author: Julien Muetton <themouette@gmail.com>
Date: Mon Aug 26 13:30:52 2013 +0200
Init as an npm package
commit f8db4d12eea0174b8e8476c21510133e3bbd27e3
Author: Julien Muetton <themouette@gmail.com>
Date: Mon Aug 26 13:24:20 2013 +0200
First commit
$ git log --graph --decorate # Display network graph
$ git log --stat # show stats
$ git log --pretty=oneline --abbrev-commit # A commit per line
git diff [file]
Show changes between two states (commits, staging, working directory...)
$ git diff diff --git a/index.html b/index.html index de3bfb6..b3d2ddf 100644 --- a/index.html +++ b/index.html @@ -36,10 +36,16 @@ some awesome content - some former content + some new content
git diff topic..master to compare branches.
git diff HEAD--8a6e1a3 to compare commits.
git stash
Stash the changes in a dirty working directory away.
$ git stash
git stash list to list stashs.
git stash apply to apply latest stash.
git stash pop to apply and delete latest stash.
git blame file
Show what revision and author last modified each line of a file.
$ git blame README 2c2513c7 (Julien Muetton 2013-08-26 18:48:45 +0200 1) # GIT basics 2c2513c7 (Julien Muetton 2013-08-26 18:48:45 +0200 2) 2c2513c7 (Julien Muetton 2013-08-26 18:48:45 +0200 3) --- 2c2513c7 (Julien Muetton 2013-08-26 18:48:45 +0200 4) 2c2513c7 (Julien Muetton 2013-08-26 18:48:45 +0200 5) ## Local first
Transitions
Branches
Linear History
Typical git repository
Tag
A Tag is a label on a commit.
Branches
The top of a linked list has a name: the BRANCH name.
Notes On Tags And Branches
- HEAD is a symbolic ref, which points to the current branch.
- Whereas branches moves, tags doesn't
git branch
List, create, or delete branches
(master) $ git branch feature
(master) $ git branch
* master
feature
(master) $ git branch -d feature
Only local branches can be managed
git checkout my-branch
Switch working directory to my-branch
(master) $ git branch feature
(master) $ git checkout feature
(my-branch) $ git branch
master
* feature
You can use shortcut git checkout -b my-branch
git rebase master
Replay the current branch on top of master.
(feature) $ git rebase master
If merge is not obvious, git asks you to solve conflict manually.
git merge
Join two or more development histories together.
(master) $ git merge feature
git merge Fast Forward
(master) $ git merge feature
git merge --no-ff
(master) $ git merge feature --no-ff
Using --no-ff keeps track of the feature branch.
git cherry-pick
Pick a commit and apply it on current HEAD.
(master) $ git cherry-pick 8a6e1a3
Note on conflicts
$ git merge iss53 Auto-merging index.html CONFLICT (content): Merge conflict in index.html Automatic merge failed; fix conflicts and then commit the result. $ git diff <<<<<<< HEAD:index.html <div id="footer">contact : email.support@github.com</div> ======= <div id="footer"> please contact us at support@github.com </div> >>>>>>> iss53:index.html
Git is verbose, but for your first conflict...
Enter remotes
Remote
A remote is a mirror of your local repository.
git clone remote [path]
Clone a repository into a new directory.
$ git clone git@github.com/themouette/fossil-core.git
(master) $ git branch -a
* master
remotes/origin/HEAD -> origin/master
remotes/origin/master
You can use http(s) or ssh to communicate with remotes.
Default remote is names origin.
git remote
Manage remote mirrors.
$ git remote
origin
$ git remote show origin
* remote origin
Fetch URL: git@github.com:themouette/fossil-core.git
Push URL: git@github.com:themouette/fossil-core.git
HEAD branch: master
Remote branch:
master tracked
Local branch configured for 'git pull':
master merges with remote master
Local ref configured for 'git push':
master pushes to master
You can add multiple remotes.
git fetch
Download objects and refs from another repository.
$ git fetch origin
Note that nothing changes in your local direcory.
git pull [--rebase] remote branch
Fetch and merge or rebase remote branch.
$ git pull --rebase origin master
Equivalent to:
$ git fetch origin/master $ git rebase origin/master
git push remote branch
Update remote refs along with associated objects.
$ git push origin serverfix Counting objects: 20, done. Compressing objects: 100% (14/14), done. Writing objects: 100% (15/15), 1.74 KiB, done. Total 15 (delta 5), reused 0 (delta 0) To git@github.com:schacon/simplegit.git * [new branch] serverfix -> serverfix
Only fast forward commits can be pushed
Extras
Submodules
Avoid submodules
git submodule add https://github.com/hakimel/reveal.js.git reveal.js git submodule update --init
Hooks
Extend Git behaviour
Client Side
Commit Workflow
- pre-commit
- prepare-commit-msg
- commit-msg
- post-commit
Email Workflow
(when using git am)
- format-patch
- applypatch-msg
- pre-applypatch
- post-applypatch
Other
- post-checkout
- post-merge
- pre-rebase
- pre-push
Server Side
- pre-receive
- update
- post-receive
Learn more on Git Hooks
Become Social
Common Workflows
Centralized Workflow
Similar to centralized version control, everybody can edit central repository.
Blessed Repository
Developer create a request to merge it's changes.
Release masters chose which requests to merge.
Lieutenant Workflow
In huge projects, lieutenants are trusted individuals in charge of reviewing requests.
Under the hood
Anatomy Of A Repository
.git directory
.git |-- branches/ |-- hooks/ |-- info/ |-- logs/ |-- modules/ |-- objects/ |-- refs/ |-- COMMIT_EDITMSG |-- config |-- description |-- HEAD |-- index `-- packed-refs
Configuration
3 Types Of Objects
- blob
- tree
- commit
Blob
Each FILE that you add to the repo is turned into a BLOB object.
tree
Each DIRECTORY is turned into a TREE object.
Obviously, a tree object can contain other tree objects and blob objects, just like a directory can contain other directories and files.
Commit
A commit is a snapshot of your working tree and a pointer to previous commit.
References
- tag
- branch
Resources
Online
- Git cheat sheet
- Pro git book
- Try git without installing.
- Make the switch