How to Git | Cecilio García

Configurations
Create Clone Repo
git status
git add
git commit
git log
git diff
git push
git checkout
git fetch merge pull
git rebase
Branches
Multiple Remotes
Submodules
Undo git merge squash
Tags
Animate Git History

Useful links:

Configurations

Tell git who are you, for the log history
- git config --global usern.name "Cecilio García"
- git config --global user.email "ceciliogarciaquiros@gmail.com"
Modify the editor used by git for the commit message
- git config --global core.editor "code --wait" Use visual studio code
- git config --global core.editor nano Use nano
Change name of default branch to “main”
- git config --global init.defaultBranch main
Change style of merge conflicts.
- git config --global merge.conflicstyle diff3 Show difference between HEAD, common ancestor and incoming branch
Local files not to be under version control. You don’t need to skip them in git add.
- Add folder name, files to .gitignore, e.g.:
  - build/
  - *.so
  - __pycache__/
- To ignore for all the repositories
  - git config --global core.excludesfiles $HOME/.gitignore put in $HOME/.gitignore those files to be globally ignored. E.g.: __MACOSX, .DS_STORE, *.swp, *~
git config --global pull.rebase true Set git pull --rebase as default when doing git pull

Create Clone Repo

Create repo locally:
- git init (inside a folder with repo name. It creates the folder .git)
- To link a new repo to github, create in github a new repo and locally do
  git remote add origin git@github.com:Ceciliogq/school2021.git (choose the repo name)
Clone existing repository:
- git clone git@github.com:Ceciliogq/school2021.git (having setup ssh in github first)
- git clone repo_address custom_repo_name (change repo name when downloading)
- git clone repo_address . (download all the files in the repo, without the source folder)
- git clone -b branch_name repo_address (clone only one branch)
With https you need to enter username and password every time
rm -rf .git remove all trace of git.

git status

See the current status of the local repo: modified files, (un-)staged files, untracked files, etc.

git status -s will show a reduced version, with one line per file. To the left, a coloured letter will tell the status of the file.

git add

git add filename Add one file to the staged area
git add . Add all the files, tracked and untracked in the current folder
git add -u Add all the modified files which are tracked
git add -p(--ptach) It allows you to choose wich junks of code wants to add. E.g. if a file contains changes that should belong to different commits.
git add foldername ':!*.h5' add folder except some kind of files
git add _ Something when there is a merge conflict???
git reset filename Remove file from the staged area. (You added the wrong file e.g.)
A alternative is doing git restore --staged filename
git mv oldfilename newfilename rename a file and put it in the staged area.
git rm filename remove a file and put the change in the staged area.
Both need to do commit afterwards
Move local changes to another branch. I did some changes but then realized they were in the incorrect branch. Stash the local changes, move to the correct branch, and pop them.
- git stash
- git checkout >correct-branch>
- git stash pop

git commit

git commit -m "Commit message" filename Will commit the added changes in filename. This will only in your local repo not yet on the internet. Without -m will promt you to write a log message. If the message contains ‘#number’, it will link to the issue ‘number’
Modify message of last commit
- git commit --amend -m "New message" This changes the hash number
- For pushed commits use git push --force remotename branchname

git log

See history of commits

git log -N Will the last N commits
git log commit1..commit2 (without spaces). Will show the commits from 1 to 2 including 2. 1 must be previous to 2.
git log --oneline Only one line per commit
git log --name-status show the name of the files changed
git log -p show the code changes of each commit
Pending git log –name-status origin/master..
git shortlog Show the contributors and their commits
- -sonly shows the number of commits
- -n ordered by number of commits
- -e add the email
- Can be combined as -sne
git log --all --decorate --graph shows a drawing of the tree structure of commits
- --decorate shows special tags of commits like HEAD
- --all shows all the refs in .git/refs as commit
- --graph show drawing of commit relations

git diff

See difference between working directory and staging area.

git diff --staged See what is going to be committed
git diff branch1 branch2 or file1 file2 difference between branches, files, commits, etc.
Save git diff in file and see in color
git diff --color source_file > output.txt
less -R output.txt

git push

Publish the commits on the internet repo

git push default repo and branch (origin/master). First time git push -u origin branch
git push reponame branchname
git push -f(--force) force the commits to be published.
git push origin --delete branchname delete the branch remotely

git checkout

git checkout commit_has load specific commit
Switching between branches has now changed to git switch
- git switch branchname
- git switch -c newbranch create new branch and change to it
- git switch -c newbranch upstream/master create new branch from another branch
git checkout hash -- filename get back a commit for a specific file
This has now been replaced by git restore
- git restore filename get last commit for a file, discard all the changes
- git restore --source=hash or branch filename restore a file to a specific commit or branch
git checkout -b new_branch remote/branchname clone remote branch
git branch new_branch create new branch pointing to current commit

git fetch merge pull

git fetch Bring changes from remote to a local staging area
git merge Merge previous changes to default remote/branch (remote, branch can be changed). The commits has are not changed, it add a “merge commit” and the rest are merged in cronological order
git merge branch_to_be_merged This will include the changes in “branch_to_be_merged” into the current branch where you are “checkout”
git merge --squas Squash all the commits in one single merge commit
git pull = git fetch + git merge default/default
git pull remote branch pull specific fork and branch

git rebase

For rewriting the git history: change commit order, drop/edit commits, merge multiple commits into one.

git rebase branch1 branch2 it will put the commits of branch2 on top of branch1
git rebase remote/branch it takes the history of remote/branch and will add the local changes (commits) on top
git pull --rebase = git fetch & previous point
git rebase -i commit_hash modify a commit interactively

Branches

git branch see current branches
Get branch from merge request
- git fetch upstream merge-requests/id/head:new_branch
- git checkout new_branch
- id is the number of the MR and new_branch the name I give to the new branch
Delete branches
- git branch -d localBranchName delete local branch
- git push origin --delete remoteBranchName delete branch remotely
Discard local changes and bring remote branch
- git fetch --all
- git reset --hard origin/master
Rename Branches
- git branch -m <oldname> <newname>
- To rename the current branch git branch -m <newname>
- To push the local branch and reset the upstream one: git push origin -u <newname>
- Delete the old remote branch git push origin --delete <oldname>

Multiple Remotes

When you want to contribute to an existing project you typically fork that repo into your username and clone your fork. That is your ‘origin’, but you can other repos and call the whaterver you want. It is common practice to name the second one as ‘upstream’.

To link your local repo to the upstream one: git remote add upstream url_of_desired_repo

You can fetch chages from upstream, merge, switch branches and push changes to it.

git remote -v to see the forks available
git remote rm upstream to remove one fork
Move branch from one repo to another:
- git remote add remoteRepo git@git/https...
- git checkout branch-to-copy
- git push reomteRepo
Set a local branch to track a remote branch. When doing git pull it will merge to this remote branch.
git branch <branch_name> -u <your_new_remote/branch_name>

Submodules

git submodule add url path Add reference to another repository at a certain commit
git clone url --recursive Clone also the submodules
git submodule update --init --recursive Update submodules (e.g. if changed on the remote)

Undo git merge squash

git fetch upstream (lscsoft/master)
git show commit1_hash This is the commit where my branch diverged from upstream/master after the merge
git revert commit1_hash This will make a series of commit to undo the merge commit
git rebase -i commit2_hash This is the previous to commit1
Delete the line of my big merge into master
git merge upstream/master
Solve conflicts if any
git add, git commit, git push -f origin/review-branch

Animate Git history

With Gource we can do beautiful animations of the history of a git repository.

The video below shows the history of the LALSuite repo from 2018 to 2021. The specific command run to produce the video was

gource --start-date "2018-01-01" --hide dirnames,filenames --seconds-per-day 0.05 --auto-skip-seconds 1 -1280x720 -o - | ffmpeg -y -r 60 -f image2pipe -vcodec ppm -i - -vcodec libx264 -preset ultrafast -pix_fmt yuv420p -crf 1 -threads 0 -bf 0 gource.mp4.

Enjoy the firecommits!

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