Quelltext der Seite Git Knowledge Base

Good introductions to Git:

* Learn Git in 20 Minutes &rarr; https://www.youtube.com/watch?v=Y9XZQO1n_7c
* Let’s Git - Versionsverwaltung und OpenSource &rarr; 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 ==

{| class="wikitable"
|+ Git Cheat Sheet
|-
! Task !! Command
|-
| Initialize empty repository || <code>git init</code>
|-
| Add file to staging area || <code>git add <file> or <pattern></code>
|-
| Remove file from staging area || <code>git rm --cached <file></code>
|-
| Commit files to repository || <code>git commit -m "<Message>"</code>
|-
| View and manage remote repositories || <code>git remote</code>
|-
| Clone remote repository || <code>git clone <URL></code>
|-
| Update remote repository from local || <code>git push</code>
|-
| Fetch objects from remote repositories || <code>git fetch</code>
|-
| Fetch objects from remote and merge || <code>git pull</code>
|-
| Create branch || <code>git branch <name></code>
|-
| Change to branch || <code>git checkout <branch></code>
|-
| Merge branch to current branch || <code>git merge <branch></code>
|-
| Show commit history || <code>git log [--oneline] [--graph]</code>
|-
| Unstage file || <code>git reset HEAD <file></code>
|-
| Discard file changes || <code>git checkout -- <file></code>
|-
| Alter last commit || <code>git commit --amend</code>
|-
| Go back to previous commit || <code>git reset <commit></code>
<code>git reset HEAD~</code>
|}

== 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

<code>git pull</code> = <code>git fetch</code> + <code>git merge</code>

{| class="wikitable"
|+ Notable Files
|-
! Location !! Filename !! Description
|-
| <code>.</code> || <code>.gitignore</code> || List of files and directories to be ignored
|-
| <code>.git</code> || <code>HEAD</code> || Contains reference to HEAD commit checksum of current branch
|-
| <code>.git/refs/heads/</code> || <code>main</code> || HEAD commit checksum of branch
|-
| <code>.git</code> || <code>description</code> || 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
 									 
{| class="wikitable"
|+ Resetting
|-
! command !! Is Default !! Changes what !! Resets Staging Area !! Reset Work Directory !! Secure
|-
| <code>git reset --soft HEAD~</code> || No || Branch HEAD || No || No || Yes
|-
| <code>git reset --mixed HEAD~</code> || Yes || Branch HEAD || Yes || No || Yes
|-
| <code>git reset --hard HEAD~</code> || 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 &rarr; 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''


[[Category:Git]]