Learn Git

Intro

• It is a standardised way of tracking your code and analyses (plus history thereof).
• Mrshu says that it's a good idea to learn Git, because it:
  • Helps avoid "versioning hell" (you know, files like essay.doc, essay_v2.doc, essay_final.doc)
  • Gives you the ability to "jump in time"
  • Helps you make your work "reproducible"
  • Makes it a bit more straightforward to work on common (larger) projects with others
• And don't forget that Git != GitHub != GitLab. Git is the technology that powers GitHub and GitLab who are "web frontends" and business who added things like pull requests.

Learn

• Start with this article that explains the main principles of Git using a fitting analogy with designing a car.
• Follow-up with reading this tutorial that sums up the very basis how to work with Git(Hub).
• For further getting a better grasp on some terms, it's worth going through this one.
• When it's time to start playing around on some examples, this interactive website is the perfect place for it.
• If it still doesn't make sense, maybe a visual tutorial good be the way to go?
• Before pushing a first commit, it might be a good idea to find out how to write a good commit message. Like this one, for example.
• If there is still anything unclear, Git docs/book will almost certainly have an answer.
• In case you wish to discover more commands that you might encounter and you are a visual learner this Visual Git Reference might be of interest to you.
• Still confused about some terms and hungry for some more (sometimes a bit technical) explanation, try How to explain git in simple words?.

Snippets

• When anything goes wrong, these code snippets come particularly handy; alternatively these from CIA.

• Make .gitignore ignore the files that were committed before added into the file:

  $ git rm -r --cached .
  $ git add .
  $ git commit -m ".gitignore is now working"
  

• Create repo from scratch through this init.sh script, based on this, which can be run through sh init.sh repo-name from directory (or better still ./init.sh repo-name if you run chmod u+x init.sh first):

  #!/bin/zsh
  
  mkdir $1
  cd $1
  
  if [ "$2" = "--p" ] ; then
      python3 -m venv .venv
    source .venv/bin/activate
  fi
  
  git init
  gh repo create $1
  git pull origin main --rebase
  touch README.md
  atom ./
  

• See your log of changes in a nice format:

  git log --pretty=oneline
  # or
  git log --oneline --decorate --graph --all
  

• Copy-paste commits from one branch to another:

  git cherry-pick
  

• Print some nice stats about your changes

  git diff main...origin/your-branch | diffstat -Cm
  git diff master 00aa0157f23f50151f74e4ba203deb8f11621946 . | diffstat -Cm
  

• Get stats for commits per person per month

  git log --pretty=format:"%h,%aN,%ad" --date=format:'%Y/%m' | awk -F, '{print $2","$3}' | sort | uniq -c | awk '{print $3","$2","$1}' > output.csv
  

• Save your work for later

  git stash # stash all files
  git stash push -m "message" [file] # stash file with message
  git stash list # check stashed files
  git stash apply stash@{0} # apply the changes
  git stash drop stash@{0} # delete stashes
  

• Find a bad commit when there is a bug, more info here

  git bisect start
  git bisect bad HEAD
  git bisect good xxxxxxx
  git bisect good|bad
  git bisect reset
  

Links

• Learn from Mrshu here
• Use Git in Python using GitPython
• Version-control large datasets, esp. in ML projects, using DVC
• Merging vs Rebasing
• Git's data model
• Git uses hashing via SHA-1 – maps arbitrary-sized inputs to 160-bit outputs (which can be represented as 40 hexadecimal characters, e.g. commit hashes) but no longer unbroken; more info in Learn about cryptographyLearn about cryptography
  Entropy
  
  Entropy is a measure of randomness
  
  
  
  
  Hashing functions
  
  A cryptographic hash function maps data of arbitrary size to a fixed size
  An example of a hash function is SHA-1, which is used in Git references
  At a high level, a hash function can be thought of as a hard-to-invert random-looking (but deterministic) function.
  A hash function has the following properties:
  
  Deterministic: the same input always generates the same output.
  Non-invertible: it is hard to f...
• There are many different workflows, i.e. practices to follow when working on big projects.
• Analyse how a Git repo grows over time