Session#6.md

Session#6

Git Version Control

A Free Open Source DVCS ”distributed version control system ”

How it Works!

• Snapshots, Not Differences

  • Compares SHA1 sum of modified files.
  • Saves the new file as a Whole "easier to retrive lost data"
  • Each Snapshot contains references to the files "to save space uses ref. only"

• Stores new versions of files only

  

• Each snapshot contains each file

  

• Everything is local “distributed”

  • Each Computer has all the history of the project
  • Makes it faster and easeir to contribute
  • Safer beacuase the data are not onlt on one repo

• Git has Integrity

  • Everything in Git is CHECKSUMMED "fast ,reliable"
  • Uses SHA-1 hash "a 40 hexadecimal char string"
  • Easy to recognize corrupted files.

• Git Generally Only Adds Data "Everything is almost reversible"

Files’ Three States

• Modified
• Staged
• Committed

Installtion

$ sudo apt update
$ sudo apt intsall git

First Time Configurations

git config --global user.name "John Doe"
git config --global user.email [email protected]
git config --global core.editor nano
git config --global merge.tool meld 

Git Help

git has a really good command manual for each command

$ git help <command>
$ man git <command>
$ git <command> -h #summarized

Important Terms

• Repository
• Index “Staging area”
• working tree “Project tree”
• Commit
• Branch
• Tag
• Master
• Head

Git Basics

Create a new repository

    $ git init # Intialize an empty/new repository
    $ git clone <URL># to Clone/Copy exsiting repository

<URL>: can be git, shh, http, https, file , etc

Doing changes in the repository

• Remove files or directories

  git rm <file name| wild card>

• Move or rename files or directories

  git mv <file directory | file name | wild card> <new directory | new file name>

Recording Changes to the Repository

• Checking status of your files

  $ git status
  $ git status -s # Summarized

  • ?? “ untracked ”
  • A “ staged ”
  • M “ Modified staged “
  • M “ Modified untracked “

  Example:

  $ git status
  $ echo 'I' > README #creates a new file
  $ git status

• Staging Modified Files

  Stage your files after adding not before

  $ git add <files|WildCards> 

  Example:

  $ git add README
  $ git status
  $ echo “USE” >> README
  $ git status
  $ git add README
  $ git status

• Ignoring Files

  A file listing patterns to match them with files in your repositories.

  File name “.gitignore”

  • .gitignore common templates

  • See man gitignore for more information

• Viewing staged and unstaged

  $ git status
  $ git diff #diffreneces between commited  and modified/untracked
  $ git diff --staged #diffreneces between commited and modified/tracked/staged

  Example 1

  $ git commit -am “cleaning the stage”
  $ echo “Git” >> README
  $ echo  “Git” > Cont.md
  $ git add README Cont.md
  $ git diff # 
  $ echo “OSC” > Cont.md
  $ git status
  $ git diff

  Example 2

  $ git commit -am “cleaning the stage”
  $ echo “1” > file
  $ git add file && git commit -m “new file”
  $ echo “2” > file
  $ git add file
  $ echo “3” >file
  $ git diff
  $ git diff --staged

• Committing Changes

  $ git commit
  $ git commit -m "short Message"
  $ git commit -am “Your Message” #Stage all untracked files and commit all files in staged area

  Example

  $ git commit -am “cleaning the stage”
  $ echo “1” > newfile
  $ git commit -am “new file”
  $ git status
  $ git add newfile && git commit -m “new file”
  # Change “newfile” and try using commit -am “changed new file”

• Commit History

  $ git log
  $ git log -p
  $ Git log -<number>
  $ git log --since <date>
  $ git log --until <date>

  <data>or <number> EX : “ 2008-01-15” or EX : "2 years 1 day 3 minutes ago"

Undoing Things

Undo add (Unstaging a Staged File)

$ git reset <files>

Amend

$ git commit --amend

Used to change your latest log message and to make modifications to the most recent commit

Undo Commit

    $ git revert <commit> # merge a previous commit with current commit into a new commit
    $ git checkout <commit> # move the Head to the specified commit and change the working set to match the commit
    $ git checkout <file> # change the file to match the commited version of the file "the Head commit"
    $ git reset --soft <commit> # the Head and the branch pointer will move to the specified commit
    $ git reset <commit> # the Head and the branch pointer will move to the specified commit and will clear the index
    $ git reset --hard <commit> # the Head and the branch pointer will move to the specified commit and will clear the index and reset the working directory to match it

- git reset:
- --soft: uncommit changes, changes are left staged (index).
- --mixed: (default): uncommit + unstage changes, changes are left in working tree.
- --Hard: uncommit + unstage + delete changes, nothing left.
- <commit>:
    - SHA1
    - Head^,Head@{number}

Remote Repositories

• Clone a Repository

$ git clone <URL>

- <URL>:
 - https://github.com/
     - git://github.com/koke/grit.git
     - [email protected]:mojombo/grit.git
     - /srv/git/project.git
     - file:///srv/git/project.git

• Showing Your Remotes

      $ git remote
      $ git remote -v

• Add Remotes

      $ git remote add <Name> <URL>

• Fetching and Pulling Repositories

      $ git fetch <remote>
      $ git pull <remote> <branch>

• Pushing into Repositories

      $ git push <remote> <branch>

Branching

• List branches

     $ git branch
     $ git branch -a

• Create new branch

  • git branch testing

  

  • switching Branch

          - “git checkout testing”
    

  

  • Commiting in a New Branch

  

  • Return to master Branch

  

  • Commiting again Branch

  

• Switch branches

     $ git Checkout <branch name>

• Delete Branches

     $ git branch -d <branches>

• Merging Branching

  • Fast-forward
  • Recursive “Three Way merge”
  • git mergetool
  • meld

• Combine Commits and Modify History of a Branch

  • git rebase

Remote Branches

Local Git Repositories

- git daemon:
 - base-path=<path> 
 - export-all 
 - reuseaddr 
 - informative-errors 
 - verbose
 - enable=receive-pack
 - You can use aliases

git aliases

- git  config --global alias.<name> ‘commands’

$ git config --global alias.serve '!git daemon --base-path=. --export-all --areuseaddr --informative-errors --verbose' 
$ git serve

Resources

• Pro GIt
• git daemon
• rest vs checkout vs revert