Git Tutorial - Commands from Beginner to Advanced Level

What is Git?

Git is a world wide populor distributed version control system which keeps track of all files in a cenrtalized location. It is a free and open source created by Linus Torvalds in 2005.

In short there will be a centralized copy (master) available in one location and the copy of the same will be copied into each user machine. All users changes will be pushed/merged into the same centrlized/parent copy (maseter) with the help of git commands (add, commit, push, pull etc.)

Advantages of Git

- Speed
- Simplicity
- Fully Distributed
- Excellent support for parallel development, support for hundreds of parallel branches.
- Integrity

Thinking in Git

Thinking in git is simple and easy by practicing it. This article covers the Git commands for beginner to advanced level. Each and every command will be presented with simple and straight forward explanation.

Git Commands

What is my git version?

Command: git --version

Show git configuration details

Command: git config --list
This command shows detailed git configuration for the branch like below.
- remote.origin.url
- user.name
- user.email
- credential.helper (Type of credential stored)

How to create an empty git repository?

Command: git init
Creates an empty repository (Folder) in the machine with the hidden git configuration files in it.

How to clone an origin branch?

Command: git clone <branch_link> <local_branch_name_optional>
It copies all the files from the specified remote branch into the current local machine folder. This stores the chain with remote branch for pushing and pulling the changes.  

Workflow of pushing changes

Modify Files > Staging > Committing > Pushing

What are my pending/modified changes?

Command: git status
Lists the modified files both staged and unstaged.

How to stage files?

Command: git add .
All the modified files will be shown in the unstaged/changes area. To push the local changes you need to stage, commit and push them. Above command will add all the files to the staging area.
Command: git add filename
If the given file name is existed in the modified list then the file will be staged.

How to commit changes?

Command: git commit -m "Commit Message"
You can only commit the staged changes. All the staged files will be committed with the above command. Make sure the files are available in staged area before running this command. Every commit will be generate with an unique hash id to address the commit. This is unique across the all the branches.

Reverting Commit

Command: git revert <commit_hash>
Every commit assigned with an unique hash id (Ex:f26ef0db7d33b46cccccda4699319ef518fdd3c7) to address or refer the commit. This is unique across the all the branches. The above command will revert the given commit.

Pushing changes to origin branch

Command: git push
Pushes all the local commits to origin branch

What are the available changes in origin and how to fecth them?

Command: git fecth
This will compare the origin branch with local branch and list out the commits or changes which are available in origin branch but not available in the local repository. These changes in origin branch can be pushed by the other users from thier local brach. This command helps in knowing what are all the incoming commits before pulling them.

How to pull the changes from origin branch?

Command: git pull
Gets all the pending commits from origin branch into the working branch.

Lis out commit history

Command: git log
Get all the detailed commits history (Commit hash, message, committed owner, committed date, files changed etc.) of the working branch.

Get names of all local branches

Command: git branch

Get names of all remote branches

Command: git branch -r

Get names of both local and remote branches

Command: git branch -a

Switch from one branch to another branch

Command: git checkout <local_branch_name>

Branching - Create a new branch from working / current branch

Command: git checkout -b <new_branch_name>

Branching - Create a new branch from another local branch

Command: git checkout -b <new_branch_name> <source_branch_name>

Branching - Create a local branch from a remote branch

Command: git checkout -b <new_branch_name> <origin/remote_branch_name>

Branching - Delete local branch

Command: git branch -d <local_branch_name>

Branching - Push local branch to remote

Command: git push origin <branch_name>
This will push the local branch to the remote which can be shared with the others.

Branching - Merge another local branch into current branch

Command: git merge <other_local_branch_name>
This compares the commit history of source branch with current branch and merges the changes from source branch into current.

Stashing - Saving Changes Temporarly

Stashing helps in saving the modified and uncommitted changes temporarly. Each stash will be stored with an index by following LIFO (Last In First Order). You can re-apply the saved stash or changes across all the branches. It supports deleting or dropping. You can create a new branch with the stash as well.

Stash the changes
command: git stash

Stash the changes with message
command: git stash save "<stash_message>"

Show all the saved stashes
command: git stash list

Re-apply most recent stash and keep it in your stack
command: git stash apply

Re-apply stash by index
command: git stash apply <index>

Apply most recent stash and then drop
command: git stash pop

Remove most recent stash
command: git stash drop

Remove stash by index
command: git stash drop <index>

Create a branch from stash
command: git stash branch <branch_name> stash@{index}

Get commit details by commit-hash

Command: git show <commit-hash>
This command gets the details of commit which are commit hash, message, owner, date, files changed along with changes.

Cherry-pick commit

Command: git cherry-pick <commit-hash>
Cherry-pick command copies the commit into the current branch. This we use to copy the commit from one branch to another branch.

What is a HEAD?

HEAD is a reference to the last commit in the currently check-out branch. When you do a new commit then HEAD will be pointed to the newly created commit.

Below command shows where and which commit the HEAD is currently pointing to
Command: git show HEAD

Show nth commit with the HELP of HEAD
Command: git show HEAD~<index>

How to rename local and remote branch?

1. Switch to the branch you want to rename
Command: git checkout <branch_name>

2. Rename the branch
Command: git branch -m <new_branch_name>

3. Push the renamed local branch to the remote and reset the upstream branch. This will create the new branch in remote with the new_branch_name and keep the old branch as it is.
Command: git push origin -u <new_branch_name>

4. Delete remote branch with the old_branch_name
Command: git push origin --delete <old_branch_name>

Batch Scripting | Batch Programming | Batch File | Batch Tutorial | Scripting Made Easy | Working with Batch Scripting

Prerequisites

- Computer programming knowledge.
- Windows command line commands basics.

What is Windows Command Prompt | Command Line | Command Shell | cmd | cmd.exe | Command Line Interpreter?

Command prompt is an executable windows application which is available on most of the operating systems. It supports a list of windows commands. Command line interface helps in performing windows operations like creating/deleting/renaming/copying/moving folders or files, open files or applications etc.

What is a batch file?

A batch file or a batch script or batch job is a file which contains the list or collection of commands which will execute sequentially from top to bottom in command window. In windows operating system a batch file stored with an extension *.bat.

Batch scripting advantages

- Run multiple processes at a time
- Perform repetitive tasks
- Back up files
- Easy to manage large processes
- Saves time by running collection of commands
- Can call one batch from another batch
- Supports the user inputs as an arguments
- Publishing applications
- Supports all the windows command line commands
- Can work with git commands (git installation required)

In this tutorial you will be introduced with the basic batch scripting commands.

Batch file commands

ECHO

@ECHO [ON/OFF] - sets the command-line settings. ON - Displays the executing commands on command window, OFF - won't displays the  commands on window.
ECHO [Text] - Print text to the screen)
ECHO. - Print an empty line to the screen
ECHO - Displays the current setting of the command-line

PAUSE

Stops the commands execution and wait for any key press.

REM

Adds comment in script file.

Example:
REM comment details will goes here

EXIT

Terminates execution and closes the command window.

Variables

Variable can be initialized with SET command.

Syntax: SET [/A] [variable-name]=value
/A - If the value needs to be numeric 

String variable: 

SET employeeName="Srinubabu Ravilla"
ECHO %employeeName%

The above script will print the "Srinubabu Ravilla" on screen. Variable can be accessed by surrounding with the %% as shown above.

String concatination: 

SET employeeFirstName=Srinubabu

SET employeeLastName=Ravilla
ECHO %employeeFirstName%+%employeeLastName%

The above script will print the "Srinubabu Ravilla" on screen by combining both first name and last name variables.

Numeric variables: 

SET /A employeeFixedPay=500000

SET /A employeeVariablePay=100000
ECHO Employee total salary: %employeeFixedPay% + %employeeVariablePay%

The above script prints the "Employee total salary:600000 " on screen.

Prompt user for input:

SET /p userInput=Enter employee name: 

ECHO User input: "%userInput%"

The above script prints the user entered input on screen.

Escape sequence

Most special characters can be escaped using the caret (^) below are the list of characters that can be escaped.

Example: 
ECHO Mobile number format ^<Country-Code^>^<10-digit-numeric-value^>

The above script will print "Mobile number format <Country-Code><10-digit-numeric-value>"

Directories

Get the current batch script execution directory:
An environment variable CD stores the current command directory
ECHO Current directory: %CD%

Windows commands can be utilize in the batch scripting. Below are the few examples.

Change from one directory to another:
cd /d c: 

 
Navigate to another directory by directory path:
SET folderPath=C:\Users - Manual path

CD %folderPath%  - With path from variable

 
Create a new folder:
md "NewFolder1234" - Create folder in current directory
md "c:\Users\sravilla\test123" - Create new folder in by path
md %directoryVariable% - Create directory from variable/user input 

 
Open Folder:
%SystemRoot%\explorer.exe %FolderPath%
%SystemRoot%\explorer.exe "C:\Users"

Start

Start command can be used to start the program
START C:\Users - Opens the directory
start notepad.exe - Opens notepad
START https://dotnetcookie.blogspot.com/ - Opens the URL in default browser
START mailto:srinubabu.ravilla@gmail.com - Creates a new email in mail application

Loops

Unlike other programming languages batch scripting supports only for loop. The definition of a loop is,  statements execution repeats until specified condition is satisfied.

Basic Syntax:
FOR %%variable_name IN list DO commands

list - List of any elements, separated by either spaces, comma's or semicolons.
command - Can be any internal or external command, batch file, list of commands.
%%variable_name - Variable declaration in loops is specified with %%variable_name instead of %variable_name%.

Looping through numbers

FOR %%x IN (1 2 3 4 5 6 3 2 1) DO Echo %%x

The above script prints all the numbers from starting to ending.

Looping through range of values 

Batch scripting supports numeric range looping. 

Syntax: FOR /L %%variable_name IN (LowerLimit, Increment, UpperLimit) Do some_code

/L - Specifies the loop  suppose to iterate through the range of values.

LowerLimit - The minimum numeric start value  

Increment - Numeric increment which adds to LowerLimit in each iteration 

UpperLimit - The maximum value in a range to limit with 

FOR /L %%Number_Variable IN (0, 2, 15) DO ECHO %%Number_Variable

The above script prints the range of values between 0 and 15 with the increment of 2 in each iteration.

Output: 0,2,4,6,8,10,12,14

Loop through files

Batch script supports looping through the files in current directory. File lookup (*.*) specified in the below command can support the wild card search like (*.jpg). 

for /r %%file_path in (*.*) do echo %%file_path  

Looping through directories/folders

Batch script supports looping through the directories (Includes sub directories) in current directory. Directory lookup ("*") specified in the below command can support the wild card search like (*.jpg). 

for %f in (.\*) do @echo %f                - Files in current directory

for /D %s in (.\*) do @echo %s         - Subdirs in current directory

for /R %f in (.\*) do @echo %f         - Files in current and all subdirectories

for /R /D %s in (.\*) do @echo %s    - subdirs in current and all subdirectories

So, this is all about the batch scripting. Please start with the basic commands and practice in you machine to get familiar understanding and effective learning.

SOLID Design Principles in C# - Liskov Substitution Principle (LSP)

Definition of the Dependency Inversion Principle?

Liskov Substitution Principle (LSP) states "If S is a sub type of T, then objects of type T may be replaced with objects of type S (i.e., objects of type S may substitute objects of type T) without altering any of the desirable properties of that program (correctness, task performed, etc.)"

Let's put this in a more simple way. Parent class object should be easily substituted with their child classes object without altering their actual behavior.

In Object Oriented Programming (OOP) parent child mapping will be achieved by Inheritance. If we do not properly utilize the Inheritance then our application would have end up with giving un-expected results. Let's look at the below requirement.

Consider an organization set's working hours for permanent employee is 40 hours and contract employee is 50 hours. Implement a service which should give employee weekly working hours by employee type. 

Permanent Employee Class

Contract Employee Class inherits Permanent Employee Class

Let's try to get the Permanent Employee hours by instantiating the PermanentEmployee.  

 

We will get the valid hours as PermanentEmployee is base class and it is pointing to the same class as well.

Now lets try to get the Permanent Employee salary by pointing derived class instance with the parent class.

This will return the invalid result as Permanent Employee hours set to 40, so here the Inheritance in not working as expected.

What is the solution?

Liskov Substitution Principle (LSP) help's in resolving this issue. By considering LSP let's do the code refactoring which should return a valid working hours for both the employees.

Abstract Class

Inheritance with the abstraction class states it can be derived by other classes and must implement the behaviors (abstract methods) defined in it.

Permanent Employee Class inherits Employee class 

Contract Employee Class inherits Employee class 

An abstract class is base class for which we can not create an object to the abstract class.

 Let's instantiate both Permanent Employee and Contract Employee classes and point or assign the object to the base class which is Employee.

 

Here which ever derived class you are instantiating and adding the reference to the base class the respective derived class methods will be called and returns the actual behavior of the derived classes methods.

Conclusion 

By following the Liskov Substitution Principle (LSP) we can achieve the  best results out of the application.

Please check my below posts on other SOLID principles for better understanding

Single Responsibility Principle (SRP)

https://dotnetcookie.blogspot.com/2019/12/solid-design-principles-in-c-single.html

Open/Closed Principle (OCP)

https://dotnetcookie.blogspot.com/2020/07/solid-design-principles-in-c-openclosed.html

Interface Segregation Principle (ISP)

https://dotnetcookie.blogspot.com/2020/07/solid-design-principles-in-c-interface.html

Dependency Inversion Principle (DIP)

https://dotnetcookie.blogspot.com/2020/07/solid-design-principles-in-c-dependency.html