wiki/wiki/linux/git_(package).md

Git (Client)

This entry deals with the Git client used in Linux-based systems. For a basic overview and the server setup of git see the corresponding entry

The client is pretty simple to understand. With only a handfull of commands you should be able to get your versioning going. For servers with web interfaces there are different cli tools to control it without using a browser.

Setup

On most linux distributions Git can be installed with the git package. The package provides a simple command line interface.

An alternative to the classical interface is the lazygit terminal user interface. Though it provides a new user interface it still uses the git package as a base.

Usage

This section addresses various use cases of git.

There is also an interactive fixup guide by Seth Robertson. Robertson also made guides on post production and best practices.

Modify a Commit Already Done

In Git it is possible to alter a commit. This can be done by using the --amend flag in the commit option. Together with the --no-edit flag it will create a new commit that will replace the old one with the same message and the newly changed files. This command will look like the following.

git commit --amend --no-edit

A graphic that visualizes the way amending works was made by jubb0bs in a Stackoverflow comment.

After amending a normal git push will not work as a commit was removed. In this case to push it has to be done forcefully.

Force Pushing

Force pushing in Git allows you to overwrite the history of a remote branch. Using the following command replaces the remote branch with your local state, even if other commits have been pushed in the meantime, which can in turn permanently remove these commits.

git push --force

Using the force command with the --force-with-lease flag, as shown in the following command, performs a safety check before overwriting. It only proceeds if the remote branch is still in the expected state and rejects the push otherwise. Most of the time, especially when using shared branches, this is generally considered the safer and preferred option.

git push --force-with-lease

Visualize Commit Graph

The commit history of a Git repository can best be visualized using a graph. This can be done by using the default git command as the following command shows.

git log --graph

This however is a bit hard to read. Therefore other tools have been created, that display the graph a bit more intuitively. One of this tools is called keifu.

Ignore files having local changes

If you need to make changes to a file that are local you can run git update-index --skip-worktree <file>. Following this the file won't show up as having changes from the upstream. Note that files tagged with this command are checked out sparsly, so you need to watch out for changes yourself if there are any. To revert this run git update-index --no-skip-worktree <file>.

Files that are marked this way can be listed by running the following command.

git ls-files -v | grep "^S"

Authentication via SSH

Authentication by default is done via a username and a password. For some services such as GitHub. it is not possible to use password as an authentication method. The other possibility to authenticate to git is by using SSH.

The following sections assumes using a Linux-based system using OpenSSH. For this a SSH certificate has to be created and added to the authentication agent. Afterwards it the public SSH key to be added to the git server. For GitHub there is a guide on that topic.

Following these the git repositories have to be cloned in a special way to use SSH instead of password and username. The following shows both the normal way and the SSH way to clone git repositories.

git clone ssh://git@github.com:tiyn/wiki
git clone https://github.com/tiyn/wiki

By using the SSH config file the clone command can be shortened to git clone github:tiyn/wiki. For this follow the corresponding section in the SSH entry. Set Host to github, HostName to github.com and User to git.

Improved git diff

There are different possibilities to improve the diff of git. One of them is diff-so-fancy which allows word specific git diff. A second and more modern option is delta which additionally allows syntax highlighting and a side-by-side view. delta also improves the git blame command, which is another reason why it is widely more popular then diff-so-fancy.

A more or less complete overview of the options was performed in an Article on Medium by Maxim Smolin.

git diff: Delta

delta first needs to be installed. Most package managers package it in the package git-delta.

Afterwards it needs to be enabled. To do this globally add the following lines to the configuration file of git, which can be found in ~/.gitconfig. Depending on the system settings and preferences the dark-mode (dark) and the side-by-side view (side-by-side) can and should be disabled.

[core]
        pager = delta
[interactive]
        diffFilter = delta --color-only
[delta]
        navigate = true
        dark = true
        side-by-side = true
        show-syntax-themes = true
[merge]
        conflictStyle = zdiff3

git diff: diff-so-fancy

diff-so-fancy is a drop in replacement for the default git diff look. It can be installed via most package managers using the diff-so-fancy package. Afterwards the following lines need to be run to complete the configuration.

# switch to diff-so-fancy
git config --global core.pager "diff-so-fancy | less --tabs=4 -RFX"
git config --global interactive.diffFilter "diff-so-fancy --patch"

# color improvements
git config --global color.ui true

git config --global color.diff-highlight.oldNormal    "red bold"
git config --global color.diff-highlight.oldHighlight "red bold 52"
git config --global color.diff-highlight.newNormal    "green bold"
git config --global color.diff-highlight.newHighlight "green bold 22"

git config --global color.diff.meta       "11"
git config --global color.diff.frag       "magenta bold"
git config --global color.diff.func       "146 bold"
git config --global color.diff.commit     "yellow bold"
git config --global color.diff.old        "red bold"
git config --global color.diff.new        "green bold"
git config --global color.diff.whitespace "red reverse"

Save HTTPS Credentials

The credentials used for HTTPS authorization can be saved with the following command.

git config --global credential.helper store

They can also be cached with the following command.

git config --global credential.helper cache

Both of these commands work globally. For local storing or caching of credentials the commands have to be adapted.