GIT Commands reference for DevOps Engineer

Dear DevOps Engineer!! this post is full of experimenting with git commands running most of them on the 'Git Bash' window in my laptop. I've collected three things about each git command.

• git command syntax
• What this git command will do - short descriptions
• An example command that I've executed
• Screenshot of that command execution

How do I Start a Fresh repository in Git CLI(local repo)?

You need to create a folder where you would like to start your coding project. The code can be web-site related where you can have multiple directories involved such as HTML files into a folder, all images to be used in the website in a folder, CSS files into a folder, etc. First, make the folder structure for you project then at the root of the project need to initialize the project.  To create empty repo or re-initializing a repo

Syntax :

git init

Note: It is always better to have a fresh directory created and then run the above command to initialize a local Git repository.

git init example

Getting a remote repository to your git client - Local system/Laptop

You can have the remote repository either public or private teams on the following SCM clouds:

1. GitHub 
2. GitLab
3. BitBucket

git clone Syntax:

git clone ssh://git@github.com/[username]/[repository-name].git

Create a local copy of a remote repository of GitHub or Gitlab. Make sure that you're doing first time in that folder, it should not have the same repo that means if your re-run the same command it cannot work.

Please make sure you have the correct access rights and the remote repository exists

Example of using gitlab URL:

 git clone https://github.com/BhavaniShekhar/vtdevops2021feb.git

Vybhava : git clone 

Syntax:

git commit -m "[commit message]"

commit changes
Example:

git commit -m "some message"

git commit command

Syntax:

git checkout -b [branch name origin/[branch name]

Clone a remote branch and switch to it
Example:

git checkout -b feature2

Differences between git checkout & switch command

Syntax:

git checkout [branch name]

Switch to a branch
Example:

git checkout

git checkout command

Syntax :

git checkout -

Switch to the branch last checked out
Example :

git checkout -

git last checkout command

Syntax:

git checkout -- [file-name.txt]

Discard changes to a file on which you are worked recently.
Example:

Syntax:

git push origin [branch name]

push to a branch to your remote repository
 Example:

git push origin slave

git push command

Syntax:

git push -u origin [branch name]

push changes to remote repository (and remember the branch)
Example:

git push -u origin feature1

git push origin command

Syntax:

git push

push changes to remote repository (remembered branch)
Example:

git push

git push command 

Syntax:

git push origin --delete [branch name]

delete a remote branch
 Example:

git push origin --delete feature3

git remote branch delete oush command

git pull command

Syntax:

git pull origin [branch name]

update local repository to the newest commit
Example:

git pull

git pull command

pull changes from remote repository Example:

git pull origin newbranch2

git remote

Syntax:

git remote add origin ssh://git@github.com/[username]/[repository-name].git
    or
 git remote set-url origin ssh://git@github.com/[username]/[repository-name].git

add a remote repository Example 1:

git remote add origin git@gitlab.com:gitops4/docker-exercises.git

set a repository's origin branch to ssh Example 2:

git remote set-url origin git@gitlab.com:gitops4/docker-exercises.git

git log

The syntax for the git log command is:

git log [--summary] [--oneline]

view changes
Example:

git log

git log command

view changes made to files or directory in (detailed)
Example:

    git log --summary

git log summary command

view changes(briefly)
Example:

    git log --oneline

git log oneline command

Syntax:

git diff [source branch] [target branch]

preview changes before merging 

References: 

 Git log command examples https://www.thegeekstuff.com/2014/04/git-log/

Git log - commit history

Here is the GitOps story! we started learning more depth of every GIT commit history using git CLI. In this post, we have touched some rea-time scenario-based question and answers with practical examples which are useful for other DevOps team members. 

The best question to help release management - who worked on the critical program/script which is in the release process? This can be found using the git log command. 

The most interesting story if someone left the company and need to know what he did in his last commit. Tracking changes all of them done by that particular user. 

The git log having many options:

1. sorting
2. filtering
3. output formatting

Let's see in detail by with experimenting each with an example.

How to get the git log in a "Sorting order"?

Here we have a couple of sorted commit history commands. 

Using the --pretty value with Oneline to going to give you the log output in simplify format.

git log --pretty=oneline
  

The output combination of COMMIT_ID COMMIT_MESSAGE | Branch level changes

How to do Filtering while getting the git-log output?

To filter out we can use different options

1. author - User name of the commit made by
2. date ranges - We have date options with --before and --after where date can be given in "YYYY-MM-DD" format
3. regular-expressions - Linux grep like option --grep that takes any text patter to filter 
4. path - file or directory path can be used to narrow down your log filtering
5. 
   

Find the commit history of a user

Here we have an option to get all changes made by a person/author. If you want to see all commits made by yourself then you can replace the "AUTHOR NAME" with your git user. name what you have configured. 

git log --author="AUTHOR NAME"

For example: Find all code changes done by user "Rajasekhar"

Find History in range of dates

You have a choice of selecting range of date before and after dates.

git log --before="date1" --after="date2"

For example: Find all commits between 19th Feb to 26th Feb 2021

Commit History with a regular expression

Git commit history can be extracted with the regular expression that matches to the word or pattern that matches the existing commit messages.

git log --grep="PATTERN"

For example, find all the 'commit's having an "adding" pattern.

 

Commit history of a given path

We can use the current work-tree contained in any one of the folders as the path to check the history of that particular directory.

git log -- [PATH]

Example for finding the git log history of file of folder as shown below:

git log -- . # current folder
git log -- WebLogic/samples # specific directory history
git log -- README.md # specific file history  

what is happening in this directory?

Knowing about a particular code file we can use -- then the filename.

For example; 

Commit History of a file

What happened since the date?

Changes from a particular "date" onwards we can get using --since option.

git log --since="YEAR-MM-DD"

For example, find all change that happen since 22-Feb-2021

Since date onwards commit changes

In most of the real scenarios we need to know the files which are changed recently. This git-log command with the oneline option and abbreviated commit id helps us to have a simple view

git log --pretty=oneline --abbrev-commit  

git log command with --abbrev-commit to short commit-id output

You can use this for more combinations as per your project requirements To get all oneliner logs with short commit id and filtered with specific author changes:

git log --pretty=oneline --abbrev-commit --author "Bhavani" 

To get all oneline logs with short commit id for all changes made for "WebLogic" pattern matched in the commit messages.

git log --pretty=oneline --abbrev-commit --grep "WebLogic" 

Further learning post:

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