What is "verion control"

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.

Without Version Control

# 2015-11-10
cp -r project project.bak
# 2015-11-11
cp -r project project.bak1
# 2015-11-12
cp -r project project.bak2
# 2015-11-15
cp -r project project.bak3
                        

Local Version Control Systems

Centralized Version Control Systems

Distributed Version Control Systems

GIT

Distributed Version Control Systems

A Short History of Git

• Linus Torvalds (the creator of Linux)
• Source Control Management
• ~2005 BitKeeper
• 2005~ Git

Git Basic

• Snapshots, Not Differences
• Nearly Every Operation Is Local
• Git Has Integrity
• Git Generally Only Adds Data

How to install

                        $ pkg install git
                        

getting started

git config --global user.email "you@example.com"
git config --global user.name "Name"
# global config in ~/.gitconfig
                        

Getting a Git Repository

$ git init
$ git add [file]
$ git commit
                        

The Three States

The lifecycle of the status of your files

.gitignore

# no .a files
*.a
# but do track lib.a, even though you're ignoring .a files above
!lib.a
# only ignore the TODO file in the current directory, not subdir/TODO
/TODO
# ignore all files in the build/ directory
build/
# ignore doc/notes.txt, but not doc/server/arch.txt
doc/*.txt
# ignore all .pdf files in the doc/ directory
doc/**/*.pdf
                        

git add

Add file contents to the index

$ git add file file1...
$ git add directory
$ git add .
                        

git rm

Add file contents to the index

$ git rm [file]
# only remove files from the index (untrack the file)
$ git rm --cached [file] 
                        

git mv

Add file contents to the index

$ git mv file_from file_to 
# equivalent to
$ mv file_from file_to
$ git rm file_from
$ git add file_to

                        

git commit

$ git commit 
-a: stage all modified and deleted path
-m: use the given message as the commit message
--amend: Replace the tip of the current branch by creating a new commit
                        

git status

$ git status -s
M README.md         # updated in index
D run.sh            # deleted from index
R src/main.js       # renamed in index
A src/index.html    # added to index
?? src/READEME.md   # untracked
                        

git log

$ git log
--all
--graph
commit 405251d689b10aba987a081589b334426968e2ac
Author: wnlee wnlee@cs.nctu.edu.tw
Date:   Thu Nov 13 15:22:07 2015 +0800

    Initial commit


$ git log --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset' --abbrev-commit
$ git config --global alias.lg "log --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset' --abbrev-commit --date=relative"
                        

git diff

git diff [commit] [commit] [file-path]
--cached/--staged
--word-diff
                        

Undoing Things

# Change preview commit again
$ git commit --amend

# Unstaging a Staged File
$ git reset HEAD file

# Unmodifying a Modified File
$ git checkout -- file
                        

git branch

Branching means you diverge from the main line of development and continue to do work without messing with that main line

git branch

git branch

# List, create, or delete branches
$ git branch
$ git branch [branch_name]
$ git branch -d [branch_name]

# switch to the branch
$ git checkout [branch name]

# create branch and switch to the branch
$ git checkout -b [branch name]
                        

git merge

merge a branch into your current branch (HEAD)

conflict

• Fast-forward
• Merge made by the 'recursive' strategy.
• Merge conflict

Merge Conflicts

• Fix Conflicts
• git add
• git commit

git rebase

Forward-port local commits to the updated upstream head

# origin
      A---B---C topic (HEAD)
     /
D---E---F---G master

# git rebase master
              A'--B'--C' topic
             /
D---E---F---G master
                        

git rebase -i [commit]

• pick = use commit
• reword = use commit, but edit the commit message
• edit = use commit, but stop for amending
• squash = use commit, but meld into previous commit
• fixup = like "squash", but discard this commit's log message

git blame

show what revision and author last modified each line of a file

git show

Show various types of objects

git stash

Stash the changes in a dirty working directory away

git tag

Show various types of objects

git reset

Reset current HEAD to the specified state

git remote

git clone

Clone a repository into a new directory

git remote

manage set of tracked repositories

git fetch

Download objects and refs from another repository

git pull

git pull = git fetch + merge

git push

Update remote refs along with associated objects

The Protocols

• Local Protocol - file://, /path/project.git
• The HTTPS Protocols - https://
• The GIT Protocols - git://
• The SSH Protocol - ssh://

Protocols