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diff --git a/slides/git/presentation.md b/slides/git/presentation.md new file mode 100644 index 0000000..efd24f2 --- /dev/null +++ b/slides/git/presentation.md @@ -0,0 +1,1028 @@ +--- +jupyter: + jupytext: + text_representation: + extension: .md + format_name: markdown + format_version: '1.2' + jupytext_version: 1.3.2 + kernelspec: + display_name: Python 3 + language: python + name: python3 +--- + +<!-- #region slideshow={"slide_type": "slide"} --> +An introduction to Git +====================== + +<center> +June 28, 2021 +</center> + +<center> +Department of Aerospace Engineering, IIT Bombay +</center> + +<center> +Prabhu Ramachandran +</center> + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Agenda +------ + +- Introduction to git +- Using github and collaborating +- Workflows + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Motivation +---------- + +<center> +<img height="80%" src="img/phd101212s.gif" align="center" /> +</center> + +<br/> +<br/> +<br/> +Credit: www.phdcomics.com + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +History +------- + +- VCS: Version Control Systems +- RCS +- CVS +- SVN +- Centralized repositories + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Distributed VCS +--------------- + +- Peer-to-Peer system +- Darcs +- Bitkeeper +- Mercurial: hg +- Monotone +- Bazaar: bzr +- Git + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Collaboration +------------- + +- Sourceforge.net etc. +- github/bitbucket etc. + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Introduction to git +------------------- + +- Version control + - save work + - review changes + - do not lose history + - share with others + - reduce mental burden + +- Distributed workflow +- Requirement for modern software development! + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + + +Basic model +----------- + +- A series of changesets (commits) +- HEAD is the last commit + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + + +Getting started +--------------- + +Setup your details: + +```bash + $ git config --global user.name "Guru Programmer" + $ git config --global user.email "your_email@youremail.com" +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Create a repository +------------------- + +Create a repo: + +```bash + $ cd my_project + $ git init +``` +Note that a `.git` directory is present! + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Help! +----- + +Find help: + +```bash + $ git help + $ git help status +``` + +<!-- #endregion --> + + +<!-- #region slideshow={"slide_type": "slide"} --> + +Status +------ + +Helpful status of repository: + +```bash + $ git status +``` + +Often provides hints + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Basic commands +-------------- + +Add a file: + +```bash + $ vim readme.txt + $ git add readme.txt + $ git status + $ git commit +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Changing the default editor +--------------------------- + +`commit` will use `$EDITOR`. Change this with: + +```bash + $ export EDITOR="emacs -q -nw" + $ export EDITOR=nano +``` + +Or : + +```bash + $ git config --global core.editor "emacs -q -nw" +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +A note on commit logs +--------------------- +Here is an example: + + First line brief <= 50 chars + + Detailed information below. Ideally wrapped to 72 cols as done + here. + + - ALWAYS leave a good log message. + - Bullet points are fine. + - Multiple paras separated by blank line. + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Review history +-------------- + +What happened: + +```bash + $ git log +``` + +- Note the commit \"ID\" +- These are unique IDs + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Notes +----- + +- What happens when you commit? +- What happens when you add? +- The staging area +- New files always must be added +- Remember to `git add`! + + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Making changes +-------------- + +Make changes: + +```bash + $ vim readme.txt + $ git status + $ git diff + $ git add readme.txt + $ git commit +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Some useful options +------------------- + +- Add all changed files and commit: + +```bash + $ git commit -a +``` + +Commit log on command line: + +```bash + $ git commit -m "Fix for bug #123" +``` + +See changes in log: + +```bash + $ git log -p +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Exercise +-------- + +1. Create a dummy repo. +2. Add some files. +3. Make different changes and commit them. +4. Review the log. + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +History +------- + +- `HEAD` is the latest +- `HEAD~1`, `HEAD~2` is one/two changes before +- You can use the commit IDs (or a unique substring) + +```bash + + $ git diff HEAD~1 readme.txt + $ git diff 737e86dd9 readme.txt +``` + +Differences between two points: + +```bash + $ git diff HEAD~2..HEAD~4 readme.txt +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Recovering old versions +----------------------- + +Get the previous version: + +```bash + $ git checkout HEAD~1 readme.txt +``` + +Same rules as before apply + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Ignoring files +-------------- + +- Add a `.gitignore` + +``` + *.dat + *.out + *.pyc +``` + +Ignores all files with these extensions + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> + +Being Lazy: Aliases +------------------- + +Convenient shorthand: + +```bash + $ git config --global alias.st status + $ git config --global alias.ci 'commit -v' + $ git config --global alias.co checkout +``` + +See `~/.gitconfig` for details: + +```bash + $ git st + $ git ci + $ git co +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Recap +----- + +- `git config` +- `git init` +- `git status` +- `git add` +- `git commit` +- `git diff` +- `git log` +- `git checkout` +- `.gitignore`: ignore files + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Deleting content +---------------- + +Removing a file: + +```bash + $ git rm readme.txt + $ git commit -m "Cleaning up" +``` + +- Does the file go away? +- Can you get back the file? + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Exercise +-------- + +1. Add a file with a few additional changes. +2. Remove it. +3. Make other changes to other files. +4. Revive the deleted file. + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Undoing +------- + +Deleted too quick: + +```bash + $ git rm readme.txt + # Oops made a mistake. + $ git checkout -- readme.txt +``` + +Phew! Saved! + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Moving content +-------------- + +Moving stuff: + +```bash + $ git mv readme.txt README.txt + $ git commit -m "Renaming readme." +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Some internals +-------------- + +- A series of changesets (commits) +- Blobs: a bunch of bytes +- Tree: + - Collection of blobs + - Other trees + +- Commits: + - Information on who committed it + - Points to a tree + - Parent to this commit. + +- Tag: + - A reference to a specific commit + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Branches +-------- + +- Why branches? + + - Cheap, super-convenient + - Allow experimentation + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Simple repository +----------------- + +This is what we had so far + + + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Branches +-------- + + + +- Can commit on either branch + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Branch basics +------------- + +- `master` is the default branch +- Create: +```bash + $ git checkout -b new_branch +``` +- List branches: +```bash + $ git branch +``` +- Note `branch` branches from current branch + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +More branch commands +-------------------- + +- Switch: + +```bash + $ git checkout master + $ git checkout new_branch +``` +- Delete: + +```bash + $ git branch -d new_branch +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Merging branches +---------------- + +- Merge changes from `new_branch` to `master`: + +```bash + [new_branch] $ git checkout master + [master] $ git merge new_branch +``` +- Always merges to current branch +- Adds the changes from that branch to current one + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +What just happened? +------------------- + + + +Let us take a look at `gitk` quickly + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Exercise +-------- + +1. Create a new branch. +2. Add some commits there (add files, edit files \...) +3. Check the logs on new branch and master +4. Merge the branch to master. +5. Delete the new branch. +6. Check logs again. + +HW: Try to delete an unmerged branch. + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +What if there are conflicts? +---------------------------- + +- Merges can lead to conflicts: + +```bash + [master] $ git merge foo + Auto-merging readme.txt + CONFLICT (content): Merge conflict in readme.txt +``` +- Edit `readme.txt` and resolve conflicts + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Resolving conflicts +------------------- + +- Look for lines like so: + + <<<<<<< HEAD + Line in master + ======= + Same line in my_branch + >>>>>>> my_branch + +- Edit and remove the markers and: + +```bash + $ git add readme.txt + $ git ci +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Recap +----- + +- new branch: `git checkout -b new_branch` +- switch: `git checkout master` +- list: `git branch` +- merge: `git merge new_branch` +- delete: `git branch -d new_branch` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Recap +----- + +- Conflicts: + - Manually fix files + - Remove markers + - Add and commit + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Collaborating +------------- + +- github.com +- gitlab.com +- bitbucket.org +- etc. +- Provide hosting for a git repository +- Plus other powerful features + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Collaboration Overview +---------------------- + +<center> +<img src="img/git_server.png" align="center"/> +</center> + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Basic ideas +----------- + +- `clone` the entire repository +- `pull` changes from server +- `push` changes to server +- Share content with other users + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Local demo +---------- + +- The principles can be demonstrated without a server! +- Consider two users: + 1. Alice + 2. Bob + +- Make a server-like repository: +```bash + $ mkdir -p server/project + $ git init --bare + $ cd ../../ +``` +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Quick demo: Bob +--------------- + +Bob: +```bash + $ mkdir bob + $ git clone ../../server/project +``` +Goes to sleep + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Quick demo: Alice +----------------- + +Alice: +```bash + $ mkdir alice + $ git clone ../../server/project + $ touch readme.txt + $ git add readme.txt + $ git ci -a -m "Initial commit" + $ git push origin master +``` +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Bob next morning +---------------- + +Bob (yawn): + +```bash + $ git pull + $ git pull origin master + $ add/commit whatever. + $ git push origin master +``` +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Working together +---------------- + +- Lets say both Bob and Alice make changes but Alice pushes first +- Git will refuse to allow Bob to `push` his changes +- So Bob will first pull: + +```bash + [bob] $ git pull origin master +``` +- Resolves any conflicts +- Then Bob can push his changes + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +# Recap +----- + +<center> +<img src="img/git_server.png" align="center"/> +</center> + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Working with remote repos +------------------------- + +Clone a repo: + +```bash + $ git clone https://github.com/FOSSEE/sees.git +``` + +Pulling changes (merges into current branch): + +```bash + $ git pull + $ git pull origin master +``` + +Fetch only gets changes, it doesn\'t merge it: + +```bash + $ git fetch +``` +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Remotes +------- + +- The name `origin` is called a **remote** +- A shorthand to refer to a repo +- One can add additional remotes + + - remote is a name for another fork/repo + - You could pull/push to these remotes + +- See `.git/config` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Sharing +------- + +- Share your changes by pushing: +```bash + $ git push origin master +``` + +- To push a branch you have made: +```bash + $ git push origin my_branch +``` +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Permissions +----------- + +- You cannot write to every repository! +- So how do you contribute? +- "FORK" the repository + - This makes a clone of repo on github + - You have write access to your fork + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Forking +------- + +<center> +<img src="img/git_fork.png" align="center"/> +</center> + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Pull-requests +------------- + +<center> +<img src="img/git_pull_request.png" align="center"/> +</center> + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Contributing to another project +------------------------------- + +- You cannot write to every repository! +- **Fork** their repository: + - Makes a copy of their repo on github + - This is your repo so you can share it + +- Push to your fork +- Pull master of upstream +- Send a pull-request to upstream + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Pull-requests (PR) +------------------ + +- Fantastic for sharing code +- Easy to review/get feedback/change +- Process: + - Make a branch locally + - Push to your fork (typically) + - Select branch on bitbucket + - "Create pull request" + - target PR to reponame/master + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Managing remotes +---------------- + +Add new remotes: + +```bash + $ git remote add <name> <server> +``` +for example: + +```bash + $ git remote add fossee git@github.com:FOSSEE/sees.git + $ git pull fossee some_branch +``` +See remotes already defined: + +```bash + $ git remote -v +``` +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Managing remotes +---------------- + +Renaming: + +```bash + $ git remote rename origin upstream +``` + +Delete a remote branch: + +```bash + $ git br -d branch_to_delete # deletes it locally + + # This deletes the branch on the server. + $ git push origin :branch_to_delete +``` + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Example: simple workflow +------------------------ + +- Single developer with repo on github: + +```bash + $ git add readme.txt + $ git commit + $ git push origin master + ... +``` +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Example: two developers +----------------------- + +- Two developers collaborating on github +- Same as Alice and Bob: + +```bash + [alice] $ git pull origin master + [alice] $ git add readme.txt + [alice] $ git commit + [alice] $ git push origin master + ... + [bob] $ git pull origin master + [bob] $ vim readme.txt + [bob] $ git commit -a -m "Update readme" + [bob] $ git push origin master +``` +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Example: contribute to project +------------------------------ + +1. Fork their repo on github +2. Clone *your* fork (origin) +3. `git remote add https://.../sees upstream` +4. Make branch locally +5. Add changes to branch +6. Push branch to origin +7. Send PR to upstream + +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Odds and ends: `add -p` +---------------------- + +Adding only parts of changes "hunks" + +```bash + $ git add -p + $ git commit +``` +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +Odds and ends: `stash` +---------------------- + +Stashing lets you stow your changes away without commiting: + +```bash + $ git stash list + $ git stash + $ git stash pop +``` +<!-- #endregion --> + +<!-- #region slideshow={"slide_type": "slide"} --> +More git resources +------------------ + +- Software carpentry lessons http://software-carpentry.org/v5/novice/git/index.html + +- Bitbucket tutorials: + + - https://www.atlassian.com/git/ + - https://www.atlassian.com/git/tutorial + +- Newbie/Github: + + - http://readwrite.com/2013/09/30/understanding-github-a-journey-for-beginners-part-1 + + - http://readwrite.com/2013/10/02/github-for-beginners-part-2 + - https://help.github.com/ + +- Quick: http://rogerdudler.github.io/git-guide/ + +<!-- #endregion --> |