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Codingones

Improve your experience using git cli

codingoneswriters profile image Codingones ・8 min read

Improve your experience using git cli

❓ Abstract

Not So Basic: Devenv is a series of tutorials in which we aim to have a nice, productive and portable development environment that takes the best of both worlds between Linux and windows.

In this third tutorial "Improve your experience using git cli" we focus on git:

  • Installation and basic configuration
  • P4merge as visual diff and merge tools
  • Some handy aliases
  • SSH authentication for GitHub and GitLab and SSH agent

📝 Overview

To complete this tutorial, you need to:

Install and configure git

git is a version control system that allows you to track every modification on your codebase. With a distributed paradigm you can use git locally, and sync changes with other repositories whenever you need.

Install

If git is not installed on your machine, you can run:

sudo apt install git-all
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Follow the instructions described in this article when you are getting started with git CLI, then you can use a lot of variables to improve your configuration.

You can specify one of the three git configuration storage options: --system, --global or --local:

  • Global configurations, for all the repositories of the current user. After you run your first git config global command, git creates a .gitconfig file for you in your home folder.
  • Global configurations, for all the repositories of all users and stored in /etc/gitconfig file.
  • Local, the default scope, stores the configuration for the current repository, in .git/config file. this configuration is not tracked.

Configure User

Git associates all commit with a user, useful when you are working in a team to see the author of a change. You have to configure your username and your email:

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

Some git commands require an editor, you can set your preferred choice with:

git config --global core.editor vim
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Configure line endings

Files use special characters to represent the end of a line so that the text editors can display the next characters in a new line. The problem is that theses special characters differ depending on the operating systems. This can lead to file execution errors. You can use git autocrlf option to fix line endings.

git documentation recommends setting autocrlf to true for Windows users so that it converts line endings to CRLF when you check out code.
I would suggest to use LF line endings even on Windows to avoid some annoying problems.
For instance, you may encounter hard to resolve bugs when running a Docker container you build locally because of files containing CRLF line endings copied into the Docker image.

You can probably configure your IDE to use LF line endings as well, so you can run the following command to make git automatically convert CRLF to LF on commit:

git config --global core.autocrlf input
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Visual diff and merge

Consider using git with CLI if you do not have a long experience with git, because it invites you to understand how it works under the hood.

That said, GUI tools can help, especially in case of conflict resolution. Many IDEs can handle that well, but it is also nice to have a tool dedicated for that purpose.

Install P4Merge

P4Merge allows you to visualize the differences between files, you can even use it to compare images. It also offers an integration with git to show differences between two versions and to resolve conflicts.

Download and install the version that match your OS. For Windows users using git through WSL, download and install the Windows version.

Diff tool

difftool is a git command that can display all the differences between HEAD and a given commit or between two commits. When you use it without arguments, it displays the current unstaged changes. It is common to run it before staging files to check that all the changes are coherent for a single commit.

Define p4merge as git diff tool, then specify the command to execute.

Here is an example for a WSL setup that uses p4merge.exe, use p4merge for other systems:

git config --global diff.tool p4merge
git config --global difftool.p4merge.cmd 'p4merge.exe $LOCAL $REMOTE'
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Then disable difftool prompt; otherwise your cli will asks you to confirm between each file display:

git config --global --add difftool.prompt false
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Now you can go to any git repository, add a modification and run:

git difftool
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p4merge will show you unstaged differences.

Merge tool

mergetool shares some similarities with difftool but it offers the ability to resolve conflict. It displays two conflicted files and help to merge them in a result preview.

Configuration :

git config --global merge.tool p4merge
git config --global mergetool.p4merge.cmd 'p4merge.exe $BASE $LOCAL $REMOTE $MERGED'
git config --global --add mergetool.prompt false
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Set mergetool.keepBackup to false to avoid preserving .orig files after performing a merge:

git config --global --add mergetool.keepBackup false
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Set mergetool.trustexitcode to true so that exit code returned by p4merge indicates merge success:

git config --global --add mergetool.trustexitcode true
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Add command aliases

When using git via CLI, you can save time by setting shortcut aliases for common git commands.

ci instead of commit:

git config --global --add alias.ci commit
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co instead of checkout:

git config --global --add alias.co checkout
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br instead of branch:

git config --global --add alias.br branch
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cl instead of clone:

git config --global --add alias.cl clone
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cp instead of cherry-pick:

git config --global --add alias.cp cherry-pick
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st instead of status, with additional options. s to have an output in the short-format, andb to show the branch and tracking information:

git config --global --add alias.st 'status -sb'
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ds instead of difftool, with additional staged option that runs p4merge to show differences between head and staged files:

git config --global --add alias.ds 'difftool --staged'
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last to show the latest commit:

git config --global --add alias.last 'log -1 --stat'
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unstage to cancel git add actions and reset all staged files:

git config --global --add alias.unstage 'reset HEAD --'
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clear to remove all the current modifications.

Warning! You cannot revert this action:

git config --global --add alias.clear 'checkout .'
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Finally, lg to display git history within a nice graph:

git config --global --add alias.lg 'log --graph --abbrev-commit --date=relative --all --pretty=format:"%C(green)%h%C(reset) -%C(red)%d%C(reset) %s %C(yellow)(%cr) %C(blue)<%an>%C(reset)"'
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Here are some details about options used in this alias:

  • graph: adds a graph to represent branches on the left of logged commits
  • abbrev-commit: displays a short commit hash instead of a full hash
  • date=relative: displays elapsed time instead of commit date
  • all: shows all commits in the history of branches and tags
  • pretty=format: displays one line commits:
    • %h: commit hash in green followed by a dash
    • %d: branch name in red
    • %s: commit message
    • %cr: elapsed time in yellow between parentheses
    • %an: author name in blue between chevrons

Check your configuration

You can display the current configuration file with:

cat ~/.gitconfig
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The output should look like this:

[user]
        name = John Doe
        email = johndoe@example.com
[core]
        editor = vim
        autocrlf = input
[diff]
        tool = p4merge
[difftool "p4merge"]
        cmd = p4merge.exe $LOCAL $REMOTE
[difftool]
        prompt = false
[merge]
        tool = p4merge
[mergetool "p4merge"]
        cmd = p4merge.exe $BASE $LOCAL $REMOTE $MERGED
[mergetool]
        prompt = false
        keepBackup = false
        trustexitcode = true
[alias]
        ci = commit
        co = checkout
        br = branch
        cl = clone
        cp = cherry-pick
        st = status -sb
        ds = difftool --staged
        last = log -1 --stat
        unstage = reset HEAD --
        clear = checkout .
        lg = log --graph --pretty=format:\"%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %Cblue<%an>%Creset\" --abbrev-commit --date=relative --all
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You can also use git config to list the current configurations:

git config -l
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Authenticate through SSH

You can use SSH to generate a key pair composed of a public and a private part.

You can add your public key on your git repository host, so that it accepts SSH connections, then you can avoid writing your email each time you need to perform an action on your remote repository.

Generate a key

Run the following command to generate your SSH key pair, then:

  • Indicates the file in which to save the key, hit enter to leave the default value
  • Type your passphrase twice
ssh-keygen -t rsa -b 4096 -C johndoe@example.com
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The key generator set your key pair id_rsa and id_rsa.pub in ~/.ssh.
Never share id_rsa file, it should stay safe on your computer.

Display the content of public id_rsa.pub key and copy the output:

cat ~/.ssh/id_rsa.pub
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Register it in your git repository host

Once you copied your SSH public key, you will register it in your git repository host.

GitHub

Log in to your GitHub account, then click on the arrow next to your profile picture on the top right of the page and select Settings in the drop-down.

Click on SSH and GPG keys on the left of the page.

Click on New SSH key and set the title that describes your machine such as Home or Work and paste the public key copied in the previous section, then click on Add SSH key.

GitLab

Log in to your GitLab account, then click on the arrow next to your profile picture on the top right of the page and select Settings in the drop-down.

Click on SSH Keys on the left of the page.

Paste the public key copied in the previous section, then set a title that describes your machine such as Home or Work, finally click on Add Key.

Try to clone a repository

You can now clone one of your repositories using the SSH link:

git cl git@host.com:johndoe/my-repository.git
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The first time you clone from your repository host, git asks you to confirm that you want to continue connecting, type yes, then you will be asked for the passphrase you entered when generating the SSH key pair.

Try to remove the repository you just cloned, then clone it again, you can see that you will only be asked for your password.

Type your password once

As you may have noticed, when using SSH link, you do not need to type your email anymore, but you still spend time typing your password.

Run SSH agent

You can enter your password once for all with the following workflow, first run:

ssh-agent
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Then copy and paste the output in your terminal. Once the three commands executed, run:

ssh-add
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This makes your SSH identity available for the current session. If you try to clone the repository again, git do not asks to type your password.

If you close your terminal, reopen it and try to clone the repository, git asks for your password since your session has been cleared.

SSH agent zsh plugin

You can further simplify the workflow by activating ssh-agent plugin in your zsh configuration:

vim ~/.zshrc
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Find the line that contains plugins=, it is probably not commented with git plugin configured. Remove the comment character, the line should look like this:

plugins=(git)
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Now add ssh-agent plugin next to git separated with a whitespace, the line should finally look like this:

plugins=(git ssh-agent)
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Save and quit the editor and close your terminal. When you open your terminal again, ssh-agent asks you to type your SSH passphrase. You can now use git without requiring typing your password. When you close and open your terminal again, you will retrieve your session. But you will have to type your passphrase when you restart your computer.

Next article

In the next article, we will focus on node.js.

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