Introduction to

I quickly commented out a bit of code and forgot it 🙈

I have a lot of local versions of files, no idea which change is where 🙉

My stuff doesn't do the same as last week 🙊

Someone else changed my stuff and I have no idea where 😤

➡ Use version control!

git init

# initialize new repository
git init

git config

# set author information
git config --global user.name "Firstname Lastname"
git config --global user.email "user@uio.no"

.gitignore

# ignore python caching files
*.pyc
__pycache__

# ignore build system clutter
build-*

# always consider files source code
!*.cpp
!*.hh
!*.py

Templates for many languages can be found here: github.com/github/gitignore

git clone

# create local copy of remote repository
git clone https://git.iws.uni-stuttgart.de/dumux-repositories/dumux.git

there is two options: https/ssh (https is easier to set up)

git clone git@git.iws.uni-stuttgart.de:dumux-repositories/dumux.git
git clone https://git.iws.uni-stuttgart.de/dumux-repositories/dumux.git

git status

git status

General information

On branch feature/init-twop-immiscible
Your branch is up-to-date with 'origin/feature/init-twop-immiscible'.

Staging area

Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

      modified:   README.md

Local changes

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

      modified:   dune.module

Not tracked by git (yet) and not ignored (.gitignore)

Untracked files:
  (use "git add <file>..." to include in what will be committed)

      tutorial/gridmanager.py

git diff

# show local (unstaged) changes
git diff
git diff <file/folder>
# show changes between two commits
git diff <commit> <commit>
...

diff --git a/run.py b/run.py
index d4801a8..4afa3d5 100644
--- a/run.py
+++ b/run.py
@@ -1,5 +1,2 @@
 # set the maxiumum number iterations (default 20)
-if args['max_num_iterations']:
-    max_num_iterations = args['max_num_iterations']
-else:
-    max_num_iterations = 20
+max_num_iterations = args['max_num_iterations'] or 20
                       

git log

# inspect history
git log
git log -5
git log --oneline

fa2c249 (HEAD -> master) Second commit
dcf9426 Initial commit

git add

# stage changes for commit
git add <file/folder>
git add -p

git commit

# create a new commit (incremental change)
git commit
git commit <file/folder>
git commit -m "[readme] update installation instructions"

git stash

# stash away local (unstaged) changes
git stash
git stash list
git stash pop
git stash pop stash@{3}
git stash drop
git stash drop stash@{1}

git checkout

# throw away local (unstaged) changes
git checkout <file/folder>
git checkout -p

git reset

# remove commits / throw away changes
git reset HEAD <file/folder>
git reset --soft HEAD~3
git reset --hard HEAD~1

git revert

# create a new commit reverting <commit>
git revert <commit>

git branch

git branch
git branch -r
git branch -a
git branch feature/my-awesome-new-solver

git checkout

git checkout <file>
git checkout <commit>
git checkout <branch>
git checkout -b feature/my-awesome-new-solver

git merge

git checkout master
git merge fix/assembly-parallel

git merge

• push your changes to a branch on remote
• open a merge request
• someone else reviews and merges

git cherry-pick

git cherry-pick <commit>
git cherry-pick -x <commit>

Conflicts: demonstration

git remote

git remote add origin https://git.iws.uni-stuttgart.de/dumux-repositories/dumux.git
git remote add somewhere <url>
git remote show
git remote show somewhere
git remote remove somewhere

git fetch

# download information from remote (without changes to local repo)
git fetch origin

git pull

git pull            # merge (fast-forward if possible)
git pull --rebase   # rebase

git push

git push
git push -u origin master
git push origin fix/assembly-parallel

Example https://gitlab.com

General rules

• Rewrite history to make your changes more understandable
• Rewriting history for local changes is ok
• Important (!): Only rewrite history for remote changes (already pushed) if you know you are the only one working on this! (Or you are in close communication with collaborators.)

git commit --amend

➡ changes the commit sha

# edit the most recent commit
git commit --amend
git commit --amend --author="Firstname Lastname <user@uio.no>"

git rebase

➡ changes the commit shas

git rebase
git rebase -i master
git rebase -i HEAD~2

git rebase | recommendations

• rebase and test before merging feature branches
• interactive rebase to clean up history (e.g. fixup commits)

git push --force

➡ be careful!

# replace origin/feature/new-solver by my version
git push --force origin feature/new-solver

Some advanced stuff

Fixing repository after things went terribly wrong

git reflog

Finding the offending commit in a large history

git bisect good
git bisect bad
git bisect start

git-LFS (large file storage)

git lfs install
git lfs track largefile.png