Git Knowledge Base
Good introductions to Git:
- Learn Git in 20 Minutes → https://www.youtube.com/watch?v=Y9XZQO1n_7c
- Let’s Git - Versionsverwaltung und OpenSource → https://open.hpi.de/courses/git2020
- Pro Git book by Scott Chacon and Ben Straub: https://www.git-scm.com/book/en/v2
Git Cheat Sheet
| Task | Command |
|---|---|
| Initialize empty repository | git init
|
| Add file to staging area | git add <file> or <pattern>
|
| Remove file from staging area | git rm --cached <file>
|
| Commit files to repository | git commit -m "<Message>"
|
| View and manage remote repositories | git remote
|
| Clone remote repository | git clone <URL>
|
| Update remote repository from local | git push
|
| Fetch objects from remote repositories | git fetch
|
| Fetch objects from remote and merge | git pull
|
| Create branch | git branch <name>
|
| Change to branch | git checkout <branch>
|
| Merge branch to current branch | git merge <branch>
|
| Show commit history | git log [--oneline] [--graph]
|
| Unstage file | git reset HEAD <file>
|
| Discard file changes | git checkout -- <file>
|
| Alter last commit | git commit --amend
|
| Go back to previous commit | git reset <commit>
|
Git Basic Knowledge
Git works with:
- Snapshots
- Most operations happen locally
A file added to a repository can have the following states:
- Modified (but not staged)
- Staged (but not commited)
- Commited
git pull = git fetch + git merge
| Location | Filename | Description |
|---|---|---|
. |
.gitignore |
List of files and directories to be ignored |
.git |
HEAD |
Contains reference to HEAD commit checksum of current branch |
.git/refs/heads/ |
main |
HEAD commit checksum of branch |
.git |
description |
Repository description |
Git Commands and How To's
Staging / Unstaging Files
git add <file>|<pattern> Add file or pattern to staging area
git reset HEAD <file> Remove file from staging area
git checkout -- <file> Discard changes in working directory
(Caution: Cannot be undone)
git status
Commit and Alter Commit
git commit -m "<Message>" Commit staged files with message git commit --amend Replace last commit (Replace message if not other changes are specified) git commit --amend -m "<Message>" Replace specifically last commit message
Reset vs. Revert
https://www.datacamp.com/tutorial/git-reset-revert-tutorial
Reset Commit
How to reset the current branch to a previous commit, or to be more precise: How to reset the HEAD pointer to a previous commit?
git reset HEAD~ The tilde character refers to the last commit before HEAD.
Two tilde characters would refer to the second to last commit before HEAD.
HEAD can be replaced by checksum of commit
| command | Is Default | Changes what | Resets Staging Area | Reset Work Directory | Secure |
|---|---|---|---|---|---|
git reset --soft HEAD~ |
No | Branch HEAD | No | No | Yes |
git reset --mixed HEAD~ |
Yes | Branch HEAD | Yes | No | Yes |
git reset --hard HEAD~ |
No | Branch HEAD | Yes | Yes | No, resets work directory |
Revert
git revert --no-commit <commit ID>
https://stackoverflow.com/questions/4114095/how-do-i-revert-a-git-repository-to-a-previous-commit --> Siehe Abschnitt git revert --no-commit
Reset vs Revert of Merge Commit
https://www.git-tower.com/learn/git/faq/undo-git-merge
Long story short:
If not pushed to remote, simply reset to the commit before the merge:
git reset --hard <commit-before-merge>
If pushed to remote repository use revert
git revert -m 1 --no-commit <commit ID>
The No-Commit option puts the previous file states in the working directory unstaged for review and later commiting.
History
git log Show commit history git log --oneline Show only one line per commit in CLI instead in viewer git log --oneline --graph Additionally show graph view git log -p git log --stat git log --pretty
Branching
git branch -a List all branches git branch NewBranch Create "NewBranch" git branch -d NewBranch Delete "NewBranch" git branch -m NewName Rename current branch to "NewName" git checkout NewBranch Switch to "NewBranch" git checkout master Switch to master branch git merge FromBranch Merge changes FromBranch to current branch git mergetool
Stash / Change Branch Without Commit
When changing branches without adding files and committing them then they will not be added to their original branch. To prevent this one can create a Work-In-Progress State and stash everything there before changing the branch. Proceed as follows:
git add . Add all files git stash Assign all changes to WIP-State to the current branch git checkout <Branch2> Change to second branch ... Work on second branch git checkout <Branch1> Return to first branch git stash apply Fetch files from WIP-State to the working directory
Remote-Repositories
git remote Show remote repositories git remote -v Additionally show names and paths of remote repositories git remote add <alias> <URL> Add remote repository at URL as alias git remote remove <alias> Remove remote repository with given alias git remote rm <alias> dto.
Clone, Fetch, Pull, Push
git clone <URL> Clone remote repository from <URL> git fetch <alias> Fetch changes from alias repo without automatic merge git pull <alias> Like fetch but with automatic merge git push <alias>/<branch> Push changes to <alias>/<branch> git push --set-upstream origin main Set upstream target alias (origin) and branch (main) git push Requires push.default configuration (see below)
Grundbefehle
git bundle create file.git --all Gesamtes serverseitiges Repository in eine Datei packen
Nützliche Programme
git gui Grafische Oberfläche für Commits gitk Grafische Oberfläche für History
Commits
Mit Texteditor
git commit Committext-Eingabe VIM-ähnlich:
Vorgehen in VIM
- I drücken → Wechselt zu Insert Mode
- Comit Text eingeben
- Esc drücken
- :wq eingeben (Speichern + Beenden)
Per Commandline
git commit -m 'change text'
Dateien ignorieren
Git-Ignore-Datei erstellen:
touch .gitignore
Beispielinhalt'
# Archiv-, Log- und Object-Dateien *.a *.o *.log # Emacs-Backupdateien (Alle, die mit ~ enden) *~ # Verzeichnisse ignorieren bin/ obj/
Installing Git
git -v Check version
Source: https://git-scm.com/download
Don't forget to configure user name and email adress like described below.
Configuring Git
Git Global Config
git config --global user.name Return user name
git config --global user.name "FirstName LastName" Set FirstName LastName as user name
git config --global user.email Return user email
git config --global user.email "example@email.com" Set example@email.com as user email
git config --global push.default matching Set push.default to matching which results in
git push always pushing to remote branch
with the same name
Git-Aware Bash-Prompt
Bash erweitern um Erkennung von Git-Archiven.
emacs ~/.bashrc
Am Ende einfügen:
# Git aware bash prompt
export GIT_PS1_SHOWDIRTYSTATE=true
export GIT_PS1_SHOWUNTRACKEDFILES=true
export GIT_PS1_SHOWSTASHSTATE=true
export PS1="${PS1::$((${#PS1}-3))}\$(__git_ps1 ' [\[\e[34;1m\]%s\[\e[0m\]]')\$ "
The Seven Rules of a Great Commit Message
Source: https://chris.beams.io/posts/git-commit/#seven-rules
- Separate subject from body with a blank line
- Limit the subject line to 50 characters
- Capitalize the subject line
- Do not end the subject line with a period
- Use the imperative mood in the subject line
- Wrap the body at 72 characters
- Use the body to explain what and why vs. how
Use the imperative mood in the subject line
Commit subject lines should be written in the imperative mood, i.e.:
- Clean your room
- Close the door
- Take the trash out
Examples:
- Refactor function X
- Remove deprecated classes
- Update getting started documentation
Goal is to have the commit subject line complete the following line in a meaningful sense:
- If applied, this commit will <your subject line here>
Examples:
- If applied, this commit will refactor function X
- If applied, this commit will remove deprecated classes
- If applied, this commit will update getting started documentation
