What is GIT Hub and how to use ?

What Is Git?

Git is version control software, which means it manages changes to a project without overwriting any part of that project.

Why use something like Git? Say you and a coworker are both updating pages on the same website. You make your changes, save them, and upload them back to the website. So far, so good. The problem comes when your coworker is working on the same page as you at the same time. One of you is about to have your work overwritten and erased.

Command Line: 

                         The computer program we use to input Git commands. On a Mac, it’s called Terminal. On a PC, it’s a non-native program that you download when you download Git for the first time (we’ll do that in the next section). In both cases, you type text-based commands, known as prompts, into the screen, instead of using a mouse.

  

Repository: 

                  A directory or storage space where your projects can live. Sometimes GitHub users shorten this to “repo.” It can be local to a folder on your computer, or it can be a storage space on GitHub or another online host. You can keep code files, text files, image files, you name it, inside a repository.

Version Control: 

                          Basically, the purpose Git was designed to serve. When you have a Microsoft Word file, you either overwrite every saved file with a new save, or you save multiple versions. With Git, you don’t have to. It keeps “snapshots” of every point in time in the project’s history, so you can never lose or overwrite it.

Commit: 

              This is the command that gives Git its power. When you commit, you are taking a “snapshot” of your repository at that point in time, giving you a checkpoint to which you can reevaluate or restore your project to any previous state.

Branch: 

            How do multiple people work on a project at the same time without Git getting them confused? Usually, they “branch off” of the main project with their own versions full of changes they themselves have made. After they’re done, it’s time to “merge” that branch back with the “master,” the main directory of the project.

Git-Specific Command

                        Since Git was designed with a big project like Linux in mind, there are a lot of Git commands. However, to use the basics of Git, you’ll only need to know a few terms. They all begin the same way, with the word “git.”

1. git config :-

                  Short for “configure,” this is most useful when you’re setting up Git for the first time.
2. git help :-

                   Forgot a command? Type this into the command line to bring up the 21 most common git commands. You can also be more specific and type “git help init” or another term to figure out how to use and configure a specific git command. 

3. git clone  <url>
                   Clones a repository into a newly created directory, creates remote-tracking branches for each branch in the cloned repository (visible using git branch -r), and creates and checks out an initial branch that is forked from the cloned repository’s currently active branch.
                   After the clone, a plain git fetch without arguments will update all the remote-tracking branches, and a git pull without arguments will in addition merge the remote master branch into the current master branch, if any (this is untrue when "--single-branch" is given; see below).

4. git status :-

                   Check the status of your repository. See which files are inside it, which changes still need to be committed, and which branch of the repository you’re currently working on.
5. git add :-               This does not add new files to your repository. Instead, it brings new files to Git’s attention. After you add files, they’re included in Git’s “snapshots” of the repository.

 i) git add <file name>

              This command is used to add a single file name into repository, that file will be available to commit, if you are not add file to repository you can't able to commit.

ii) git add -u

               This command is used to add all modified files to repository.

iii) git add .

               This command is used to add all modified and newly added files to repository.

5. git commit -m "commit message"

                        Git’s most important command. After you make any sort of change, you input this in order to take a “snapshot” of the repository. Usually it goes.
6. git push origin <branch name>
                        If you’re working on your local computer, and want your commits to be visible online on GitHub as well, you “push” the changes up to GitHub with this command.                      
7. git branch :-

                   Working with multiple collaborators and want to make changes on your own? This command will let you build a new branch, or timeline of commits, of changes and file additions that are completely your own. Your title goes after the command. If you wanted a new branch called “cats,” you’d type git branch cats.
8. git checkout <branch name> :-
                   Switch branches or restore working tree files.
     Ex: If you are current working directory master, if you want to switch from master to sandbox.
              git checkout sandbox
   If you want to restore of current modified files to previous stage use the below command

              git checkout <file name> 

   To revert all modified file to its previous stage use the below command

             git checkout .

9. git pull origin <branch name>
                If you’re working on your local computer and want the most up-to-date version of your repository to work with, you “pull” the changes down from GitHub with this command.
10. git merge <branch name>
                When you’re done working on a branch, you can merge your changes back to the master branch, which is visible to all collaborators.
  Ex: you are currently working on feature branch i.e your branch xyz name.
would take all the changes you made to the “xyz” branch and add them to the master.
                 git merge xyz
11.  How to delete a branch from local repository ?
         git branch -D <branch name>
12. How to take particular commit from one branch to another branch ?
         git cherry-pick <commit-sha>
      commit-sha - take from original branch which commit you want.
      Below is the image where to take commit sha
       (deff1f5b3a86bea8128e8eb18f689bc74ba0e213)
13. How to save your local changes temporarily in your local repository ?
      git stash     
     When ever you want to pull out your changes we can use the below command
      git stash apply     
     Above command will pullout your last stashed files.
      git stash list     
      Above command will show all the local stashed commits.
      If you want to pullout specific local commit we can use below command
      git stash apply stash@{0}
      stash@{0} - this is the latest local stashed commit.
      {0} - here we can also pass specific stash number to pop out previous changes like                  below.       Ex :- git stash apply stash@{1} 

14. If you want to fix up your latest commit, you can undo the commit, and   
      unstage the files in it, by doing:
      git reset HEAD~1
      Below is the command we can use to reset N number of last commits.
      git reset HEAD~N
      If you want to get rid of your latest commit, and do not want to keep the code
      changes, you can do a "hard" reset.
      git reset --hard HEAD~1

15. To remove untracked files from git use below command

         git clean -fd