1. git config

This command used to get and set configuration variables that control all aspects of how Git looks and operates. Use --list to get all configuration as following command:

git config --list

Use the following two commands to set name and email in global level:

git config --global user.name "John Doe"
git config --global user.email johndoe@example.com

See also:
Getting Started - First-Time Git Setup
Bitbucket Tutorial

2. git init

This command is used to create an empty Git repository. Simply run the following command to initialize Git repository:

git init

To start a new Git repository for an existing code base, run the following commands in the main folder of our code base:

git init
git add .
git commit

See also:
git init docs

3. git status

This command is used to display the state of the working directory and the staging area, including which changes have been staged, which haven’t, and which files aren’t being tracked by Git.

Run the following command to see the state of our repository:

git status

See also:
Git Status: Inspecting a repository

4. git add

This command is used to move modified files to staging index which is area where Git stores files that is ready to commit.

Run the following command if we want to move all modified files into staging index:

git add .

Or run the following command to add specified files, for instance we want to add index.html and css/site.css files:

git add index.html css/site.css

To unstage files in staging index, run the following command:

git reset HEAD index.html

The preceding command will unstage index.html from staging index since HEAD is the last commit of the current branch.

See also:
git add docs
Unstage Git

5. git commit

This command is used to commit all files in staging index. We must provide a descriptive message when committing the staging index, for instance add unit test for GetUser() function

Run the following command to commit staging index in Git:

git commit -m "<descriptive message>"

See also:
git commit docs

6. git clone

This command is used to grab a complete copy of another user’s repository. In GitHub, use pattern https://github.com/USERNAME/REPOSITORY.git as target repository.

For instance, if we want to clone https://github.com/WisnuAnggoro/hello-world to our active local directory, simply run following command:

git clone https://github.com/WisnuAnggoro/hello-world.git

See also:
Fetching a remote
git clone docs
How do you clone a Git repository into a specific folder?

7. git fetch

This command is used to grab all the new remote-tracking branches and tags without merging those changes into our own branches.

To fetch remote repository, we need to specify remote-name as the target. origin is common remote name. Run the following command to fetch all branches from remote repository (origin):

git fetch origin

We can also fetch spesific remote branch to local repository. For instance, the following command will only fetch master branch in origin:

git fetch origin/master

See also:
Git Basics - Working with Remotes

8. git remote

This command is used to add a new remote. Run the following command to create origin remote name:

git remote add origin https://github.com/user/repo.git

To find out our remote name, use this command:

git remote -v

See also:
git remote docs

9. git merge

This command is used to combine our local changes with changes made by others.

Run this command to merge remotename/branchname to our active local branch:

git merge remotename/branchname

See also:
git merge docs

10. git pull

11. git push

12. git branch

This command is used to list, create, or delete branches. To list local branches only, simply run the following command:

git branch

To list all branchss in both local and remote, run the following command:

git branch -a

When listing all branches in both local and remote repositories, press d to continue to next list and press q to quit the list.

To delete local branch, we can run the following command:

git branch -d [branch_name]

The -d argument stands for --delete which will delete the local branch only if we have already pushed and merged it to remote branches.

Another delete branch command is as follow:

git branch -D [branch_name]

The -D argument stands for --delete --force. The preceding command will delete branch_name branch regardless of its push and merge status.

For SAFETY REASON, please use only -d argument when deleting local branch.

See also:
git branch docs
How to get the current branch name in Git?
Delete a local and a remote GIT branch

13. git show-branch

This command is used to show branches and their commits. Just simply run the following command to show all branches and their commits:

git show-branch

See also:
git show-branch docs

14. git checkout

This command is used to switch to different local branches. Run the following command to switch to other-branch:

git branch other-branch

To create and switch to a new-branch, run the following command:

git branch -b new-branch

See also:
git checkout docs

Source links:
Essential git commands every developer should know
Git for beginners: 12 commands you need to know
Most Basic Git Commands with Examples – a Welcome Introduction to Git