Basics

Git overview

Picture 1:

Working dir    Git database   Remotes
-----------    ------------   -------
project/       project/.git   git@git.chalmers.se:user/project
- README                      https://github.com/joe/project
- File1
- Dir1/File2

Picture 2: a version tree

* - * - * - * - * main
    |           \ * - * - * develop
    * - * - * experiment

Commit identifiers: <commit>

• hash (absolute) 4fab561
• tag (symbolic, absolute) <tag>
• branch name (tip/leaf) <branch>
• branch in a remote <remote>/<branch>, e.g. origin/master
• HEAD, HEAD~1, ... (relative to current branch)

Starting a git project

• git init
• git clone <remote>

Remotes

• Remotes have symbolic identifiers, e.g.:

    <remote>  <url>
    origin    git@git.chalmers.se:user/project
    joe       https://github.com/joe/project

  origin is default remote.

• git remote -v: list remotes

Commits

Changes in the working directory are first added to the staging area (the index) and then bundled into a commit. Usally, this is done with GUI support.

• git add <file> : add a new file or add the changes made in the file

• git commit -m <msg> : create a new commit from the staged changes

• git commit --amend : add staged changes to the last commit

• git push : push current branch to its remote (default origin)

• git pull : pull current branch from its remote

Tags

• git tag -v : list tags
• git tag -a <tag> -m <msg> : add new tag named <tag> with message <msg>
• git push --follow-tags : push "missing but relevant" tags to origin

Somewhat advanced

Branches

Default branch is often named master or main.

• git branch -v : list branches

• git branch <branch> : fork of new branch, but stay on current branch

• git checkout <branch> : switch to existing branch

• git checkout <commit> : switch to an arbitray commit in the commit tree

• git switch -c <branch> : create a new branch at the current commit and switch to it

• git checkout -b <branch> : same

• git push <remote> <branch> : push branch to remote

• git push -u <remote> <branch> : push branch to remote which is set as default remote

• git pull <remote> <branch> : pull remote branch into current branch

Pulling with conflicts

• git pull --ff-only : only pull if remote does not have new commits
• git pull --merge : pull and create a merge commit reconciling remote and local commits
• git pull --rebase : pull, but rebase current branch while adding commits from remote

Merging

• git merge <branch> : merge <branch> into the current branch E.g. if you are on a feature branch, git merge master will merge the changes from master into your feature branch.
• git rebase <branch> : merge <branch> into the current branch, keeping your commits on top
• git rebase -i <commit> : interactive rebase, allows to modify your commits

Undoing

• git revert <commit-range> : create a commit that undoes the changes of the given commits
• git reset --soft HEAD~1 : undo the last commit, keep changes in the working dir
• git reset --hard <commit> : reset the current branch and working dir to a different commit
• git reflog : show latest history

There is also git stash, but you need to know what you are doing...

Managing remotes

• git remote -v : list remotes
• git remote add <remote> <url> : add new remote to the list
• git remote rename <remote1> <remote2> : rename remote <rid1> to <rid2>
• git remote set-url <remote> <url> : bind remote to new url