What is Git?

Title Text

which means...

(almost) everything is local

everything is fast

every clone is a backup

work offline

How Git works?

Snapshot 1

Commit

Takes snapshot of your current work state

Snapshot 1

Commit

Commit

Snapshot 2

Snapshot 1 

Commit 1

cd3 - sha

Snapshot 2 

Commit 2

bc9 - sha

Uniquely Identify a work state

Next Steps

Set config

Set name

   $ git config --global user.name "Ankur Garg"

Set email

  $ git config --global core.editor "vim"

Set editor

   $ git config --global user.email "ankurgarg101@gmail.com"

Check config

  $ git config --global --edit

Check status

 
  $ git status

git add

Add a file to staging area

   $ git add .

Adds all file in repo to staging area

  $ git add filename

Adds mentioned file to staging area

The path to commit

git commit

Creates a snapshot of staged files

  $ git commit -m 'Describe what you changed here, this is called commit message'

Amend commit

Change the previous commit description or content if changes are not pushed

  $ git commit --amend

git diff

Shows modifications made with respect to previous snapshot/commit

   $ git diff

HEAD

HEAD refers to the current snapshot/commit

So HEAD is a pointer that points to snapshot we are at in repository 

HEAD^

Refers to previous commit 

HEAD~n

n is an integer and this refers to  nth last commit

$ git log

commit 19f2a02d7caa83824dd774133e301a516cd0cd24
Author: Ankur Garg <ankurgarg101@gmail.com>
Date:   Wed Jan 28 14:16:40 2015 +0530

    Edits config

commit 51cd5f0a7cd9183a7b56958b1e400b495f103ffc
Author: Ankur Garg <ankurgarg101@gmail.com>
Date:   Wed Jan 28 14:16:15 2015 +0530

    Add main helper

commit 00d06580e52a54376c68440fbbfce5e09e35e81c
Author: Ankur Garg <ankurgarg101@gmail.com>
Date:   Wed Jan 28 13:47:33 2015 +0530

    Add index.md

Edits config - HEAD

Add main helper - HEAD^

Add index.md - HEAD~2

git reset

Dangerous!

  $ git reset --mixed HEAD

Restores current state of project to a desired state

Unstage files from index and reset pointer to HEAD

  $ git reset --soft HEAD

Moves HEAD to specified commit reference, index and staging are untouched

 $ git reset --hard HEAD

Removes all changes and reset pointer to HEAD

git reset

$ git status -s
 M README
 M hello.rb
$ git add .
$ git status -s
M  README
M  hello.rb
$ git reset HEAD -- hello.rb 
Unstaged changes after reset:
M hello.rb
$ git status -s
M  README
 M hello.rb

git reset --soft

$ git status -s
M  hello.rb
$ git commit -am 'hello with a flower'
[master 5857ac1] hello with a flower
 1 files changed, 3 insertions(+), 1 deletions(-)
$ git status
# On branch master
nothing to commit (working directory clean)
$ git reset --soft HEAD~
$ git status -s
M  hello.rb

git reset --hard

$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
# modified:   README
#
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
# modified:   README
#
$ git reset --hard HEAD
HEAD is now at 5857ac1 hello with a flower
$ git status
# On branch master
nothing to commit (working directory clean)

git branch

Shows the list of branches

master is the default branch in a new repo

git branch branchname

Creates a branch with specified branchname

git checkout branchname

Shifts to specified branch

git merge

Merges two branches into each other

git rebase

Forwards commits of a branch to head?

$ git checkout master
$ git rebase branchname

Suppose there were 3 commits originally A, B and C:

Then developer Santa created commit D, and developer Banta created commit E:

Obviously, this conflict should be resolved somehow. For this, there are 2 ways:

Merge

Rebase

We create commit R, in which actual file content is identical to that of merge commit M above. But, we get rid of commit E, like it never existed. So simply HEAD is moved forward to include E in R

When do you need branches?

• Try out an idea

• Issue fixes

• Adding a feature

• Collaborating with others

Remotes

These are copies of a repo somewhere on internet

Remotes

Default remote is named as origin by git

git clone

Used to get a local copy of repository from a remote

$ git clone git@github.com:sdsmdg/cognizance.git

$ git clone http://github.com/sdsmdg/cognizance.git

Can use various protocols like SSH, HTTP to clone

git fetch

Gets latest commits from a remote

(Default to origin)

$ git fetch

$ git fetch remote_name

Can use various protocols like SSH, HTTP to clone

git pull

Get latest commits from a remote and merge them into current branch

(Defaults to origin)

$ git pull
Updating 853a38b..30eb5d8
Fast-forward
 config/config.php | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

$ git pull remote_name

git push

Push your commits to a remote. Commits must be in straight line from the latest commit at server

(Defaults to origin and current branch)

$ git push
Counting objects: 25, done.
Delta compression using up to 2 threads.
Compressing objects: 100% (25/25), done.
Writing objects: 100% (25/25), 2.43 KiB, done.
Total 25 (delta 4), reused 0 (delta 0)
To git@github.com:ankurgarg101/muzi-android.git
 * master -> master

$ git push remote_name branch_name

push rejections

Sometimes when your local repo is not in sync with remote, remote will reject your push. So always pull before push and solve any merge conflicts

$ git push origin master

To git@git.sdslabs.co.in:muzi.git
 ! [rejected]        origin/master -> origin/master (non-fast-forward)
error: failed to push some refs to 'git@git.sdslabs.co.in:muzi.git'
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Merge the remote changes (e.g. 'git pull')
hint: before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

$ git pull
Updating 853a38b..30eb5d8
Fast-forward
 config/config.php | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

$ git push

Updated origin/master -> origin/master

git remote

Used to handle various remotes

$ git remote -v

$ git remote add remotename some_url_here

List all remotes

Adds a remote

$ git clone git@git.sdslabs.co.in:muzi
Cloning into 'muzi'...
remote: Counting objects: 10058, done.
remote: Compressing objects: 100% (4088/4088), done.
remote: Total 10058 (delta 6184), reused 9482 (delta 5739)
Receiving objects: 100% (10058/10058), 28.49 MiB | 3.04 MiB/s, done.
Resolving deltas: 100% (6184/6184), done.
Checking connectivity... done.

$ ls
muzi

$ cd muzi

$ ls
admin  ajax  api.php  chrome  config  css  docs  favicon.ico  Gruntfile.js  images  js  layout.html  node_modules  
package.json readme.mkd requests.php  schema  social  stats  swf  tests  vendor  widget  zune

$ git remote -v
origin	git@git.sdslabs.co.in:muzi (fetch)
origin	git@git.sdslabs.co.in:muzi (push)

$ git remote add gh git@github.com:apsdehal/muzi.git

$ git remote -v

gh	git@github.com:apsdehal/muzi.git (fetch)
gh	git@github.com:apsdehal/muzi.git (push)
origin	git@git.sdslabs.co.in:muzi (fetch)
origin	git@git.sdslabs.co.in:muzi (push)