In this series the main focus was to build an simple pascal interpreter by python which can execute simple pascal codes like mathematical operations and procedure calling. This series introduced me lots of thing like scanner, token, parser, interpreter and grammar, etc. At first I was thinking that I will not be able to complete the series properly as I didn’t know anything about interpreter and compiler but as move forward in this series things get cleared because everything was elaborated properly. Whenever I stuck at any point I search it in the internet and try to find the proper solution. For me in this series the most interesting part was the grammar of any programming language and how they help.
In this series I also learned how to write better commits so people can understand my code and also learned how to reset my commit to previous commit when I commit wrong things or made any bad commit message. Here you can see my commits.
Pull request let you tell others about changes you’ve pushed to a github repository. Once a pull request is sent, the maintainers of that project can review the changes and discuss for modifications, and even push commits if necessary and once everything is ok they can accept that pull request and all your changes will be merged with the upstream project. Below there are set of instructions that will describe how to create pull request.
Fork the Repository
The first step should be creating a copy of a repository. You can fork a repository on GitHub by navigating with your browser to the GitHub URL of the open-source project you would like to contribute to.
GitHub repository URL contains both the username of the owner of the repository and the name of the repository. For example, below github url aniruddha2000 is the username and the hello-world is the name of the repository.
When you go to that url on your browser you will see a “Fork” button on your upper right hand side of the page.
Click the fork button and start the forking process.
Once the process is done, your browser will go to a screen similar to the repository image above, except that at the top you will see your username before the repository name, and in the URL you will see your username before the repository name.
Clone the forked repository
Now you have to clone the repository in your local machine that you have forked. In order to do that you have to use git clone command. Execute below command in your terminal.
Whenever you work on a collaborative project you and other programmers contribute to the repository will have different ideas for new features or fixes. So it is recommended that you should always work on a new branch and make pull request to the upstream project from that branch and this process will help you to work nicely will all contributors. Execute below command to create a new branch.
$ git checkout -b new-branch
Switched to branch 'new-branch'
Make changes locally
Once you have modified all necessary files you should add them git add and commit by git commit -m. After committing you have to push the changes in the ‘new-branch’. Execute below command for this operation.
$ git push origin new-branch
Create Pull Request
Now you can create a pull request to the upstream project. You can navigate to your forked repository and click the “New pull request”.
Once you have chosen, for example, the master branch of the original repository on the left-hand side, and the new-branch of your forked repository of the right-hand side, you should see a screen that looks like this:
Add the necessary comment and then click the “Create pull request” button. Now go the pull request section of the upstream repository and you will see your pull request is there.
If you are working on a project then you have to maintain it properly and that’s why we use git as our VCS(version control system) and github or gitlab as our cloud service where we store all our code remotely. Below there will be some basic git command and their description.
Initializing git repository
When you first start a project using git you have to initialize the git in side your project directory.
$ cd my_folder
$ git init
Initialized empty git repository in my_folder/.git/
Suppose if you want to work on a project that is already on github so in order to contribute to that project first you have to clone that repo to your local machine. Here git clone comes to help you in that.
If you want to check the status of a repository like which files have added and deleted and modified then you have to execute the below commands. It will also show the tracked and untracked files of the repository.
$ git status
On branch master
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)
no changes added to commit (use "git add" and/or "git commit –a")
Adding files to staging area
If you add a new file to your repository or you have modified some files then before committing you have to move those files to staging area. Here you have certain cases like you want to add files to staging area by one by on or you want to add all files to staging or you want to add all tracked files to staging area except untracked files. Below commands for all cases.
$ #Add specific file to staging area
$ git add [file_name]
$ #Add all new and changed file to staging area
$ git add -A
$ #Add all tracked files to staging area
$ git add -u
After adding files to staging area you have to commit those changes. Basically you are saving those changes as commits. Every commits has it’s commit message and unique commit ID.
$ git commit -m [commit message]
Removing files or folders
Suppose you have to delete some files from index which is not needed then you have to tell git to remove those and here git rm comes to help you.
$ git rm -r [file-name]
It is recommended that you should not change directly in the master branch. When you are experimenting something or adding any feature then always you should create a new branch and make changes there. So bellow command is showing you how to create a new branch.
$ git checkout -b <your_branch>
Switched to a new branch "your_branch"
Now type git branch to see all local branches. And if you want to see all the branches include local and remote then you have to type git branch -a. Now if you again want to come back to your master branch then you have to type below command.
$ git checkout master
Switched to branch 'master'
If you want to switch to the last checkout branch then type git checkout -. Now sometimes you have to delete a specific branch so in this case you have two branches one is in your local machine and one is in your server.
$ #delete your local branch
$ git branch -d <your_local_branch>
Deleted branch <your_local_branch> (was 4335a0a).
$ #delete your remote branch
$ git push origin --delete <your_remote_branch>
When you have finished your all features and changes in your branch it is now ok to merge with master branch. In order to merge any branch with master branch there we execute the below command.
`Basically in merging there is two branches one is source branch and another is target branch and in the above scenario the master branch is target branch and other is source branch. If you want to do the above operation in one line then you can do –
git merge [target branch]
Use git stash when you want to record the current state of the working directory and the index, but want to go back to a clean working directory. The command saves your local modifications away and reverts the working directory to match the HEAD commit. And use git stash clear to remove all stashed entries.
Sharing & updating project
After all committing stuff it is the time to push the changed to the remote server or otherwise if your local computer get disturbed you will loose all changes. Use the below command –
$ git push origin <your_branch>
Sometimes you are just working on a specific branch for a long time and it is possible that git will remember the branch name for you. Use git push -u origin <your_branch> to make git remember your branch name. After this you just have to execute the command git push and it will automatically push the commits in the remembered branch.
Now suppose you have two laptops and from both you are maintaining the project so it is very necessary for you that you keep updated the project in the both laptops. So git pull will update the local repository to the latest commits.
So git has local repository and remote repository so when ever we push something it will go to the remote repository. So it is very important to tell git that what is our remote repository. In order to add the remote repository we execute the bellow commands –
Sometimes we clone the repository in the https format url or we have set the remote url in https format but we are planning to switch to ssh. Then we will execute the below command and everything is changed . Below we are switching to ssh remote url.
If you wand to see commit history then I already published a blog about git log you should checkout. Now if you want to see what you have changed after the last commit then do git diff. It is good to see the changes you have made in the feature branch before merging to the target branch. Execute the below command for that –
The purpose of any version control system is to record changes to your code. This gives you the power to go back into your project history and see who contributed what and when and figure out where bugs were introduced. But, having all of this history available is useless if you don’t know how to navigate it. That’s where the git log command comes in. Below various git log options that will be very helpful while maintaining a big project:
The --oneline option will give you a output of commits to a single line. By default it will show you the commit ID and first line of the commit message.
aniruddha ~/Desktop/foobar master
$ git log --oneline
505a2c6 (HEAD -> master) Add the file hellomars.txt and update helloworld.txt
fb8c32d First commit
The most basic filter that git gives us the limit the number of commits. You can pass -<n> after the git log.
$ git log -3
When you are looking for commits created by a specific person then --author="name" will be the option you have to use. This will return all commits matches with the author name you have given.
$ git log --author="Aniruddha"
You can use regular expressions to search for commits. In the below example the following commands searches for commits by either Aniruddha or Sayan.
$ git log --author="Aniruddha\|Sayan"
By commit message
To filter the commits by their commit message, use the --grep flag. This works like the --author flag discussed in the above but it matches against the commit message instead of the author.
$ git log --grep="First"
Some times you are only interested in changes that happened to a particular file. To see the history related to a file you just have to to pass the file path. Below we want to see the commits related to foo.py.
$ git log -- foo.py
See changed file names
If you want to see the files you have changed according to your git commit then execute the below git command.
SSH is a tool by which we can create a secure connection between the client and server. Basically it is an asymmetric type encryption that creates two key one is public and one is private. Public key can be distributed publicly and it is used for encrypt the data and the private key have to be kept secret for decrypting the data. Below commands will create the ssh keys:
$ ssh-keygen -t rsa -C "email@example.com"
Generating public/private rsa key pair.
Enter file in which to save the key (/home/ani/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/ani/.ssh/id_rsa.
Your public key has been saved in /home/ani/.ssh/id_rsa.pub.
The key fingerprint is:
The key's randomart image is:
| . ..oo..|
| . . . . .o.X.|
| . . o. ..+ B|
| . o.o .+ ..|
| ..o.S o.. |
| . %o= . |
| @.B... . |
| o.=. o. . . .|
| .oo E. . .. |
Now you have created a pair of keys and you have to add the public key in the github. Follow below instructions after doing the above the task –
Go to your github page and open settings.
Now click the SSH and GPG keys.
Now click New SSH key.
In the title field add a relevant title fr your key. Like if you are using Linux on your PC the give a title like “Linux PC”.
Then paste your public key in the box.
Then click Add SSH key.
If it ask for your password then confirm your password.