Git Skillz Session Tutorial Repo

What is git and why do I care?

Collaboration
Versioning

How does git help?

You get your own copy of all files in a special folder on your computer called a git "repository" or "repo" for short
Everyone else also gets a the exact same copy of those files in their own repo
Each person can work independently on all files in their respective repo
Your git repo tracks all changes you make to any files
You save your changes with a git "commit" and you can back them up to the cloud - or "remote" - with a git "push"
Git "fetch" allows you to review all changes made by others before accepting - or "merging" - them into your repository
Git helps you resolve any collisions where 2 people edited the same file on each of their respective computers. It does deep comparisons between versions using git "diff" the two files and walks you through deciding which one you want
Git also allows you to have multiple versions of your entire repo - or "branches" - that you can switch back and forth between
And lastly, git, if used correctly, will practically never let you lose data; you can always recover "lost" changes.

That's crazy. How does git do all of that!

Well we've already started to learn about the model and terminology git uses above!
But as a reminder, here's a recap of some terminology:
- Things:
  - repository - code base stored in a special folder
  - commit - the set of changes you made to one or more files (analagous to the changes make to a word doc in between saves)
  - branch - an easy-to-remember label given to a particular commit
  - remote - a url to someone else's copy of the repository
- Actions:
  - add - instruct git to start tracking a new file
  - checkout - change to a different snapshot (commit/branch) of the repo
  - push - pushing your changes to a particular remote
  - fetch - download someone else's changes from a particular remote (but don't accept them into your repo yet)
  - merge - accept changes into your repo
There are more terms that you'll come to know and love, like "rebase" and "reset" as you get into more and more advanced git usage

As an aside, there are all sorts of mental models to use when learning git. This tutorial is just one of them. If this one doesn't jive with you, please just let me know and I'd be happy to help with any number of other mental models

A walk through a git example

Tell git who you are!

  git config --global user.name "First Last"
  git config --global user.email "first.last@skyspecs.com"

Get me a repo

git clone https://github.com/jbendes/git-skillz.git

Modify some files

cd git-skillz; echo "test" > example-file.txt;

See the status of any changes you've made to the repo

git status

"Stage" your changes

git add example-file.txt

See the status now that you've "staged" your changes

git status

Save your changes

git commit --all --message "I just made my first git file!"

Push your changes to a remote

git push origin master

See which human-readable version of the repo you're in

git branch

Make a new branch

git branch learn-about-branches

See all branches in your repo

git branch -a

Switch to a different commit/branch

git checkout learn-about-branches

See all branches in your repo

git branch -a

Fetch anybody else's changes

git fetch origin

Let's step into the 4th dimension!

gitk --all

Normal git workflow to preserve a clean tree

    git checkout master
    git branch feature1
    git checkout feature1
    echo "did some work" > example-file2.txt
    git add ./example-file2.txt
    git commit --message "Did work"
    echo "did some more work" > example-file3.txt
    git add ./example-file3.txt
    git commit --message "Did more work"
    git checkout master
    git merge --no-ff feature1 --message "Solved world hunger"
    git branch --delete feature1
    gitk --all
    git push origin master

Advanced git commands

See a unique id - or "hash" - for a branch/commmit

git rev-parse learn-about-branches

Move the non-common history of all of my changes on "top" of another branch/commit

git rebase master

Move a complex section of history on "top" of another branch/commit

git rebase --rebase-merges --onto master <COMMIT BEFORE START> <LAST COMMIT>

Grab a commit and put it on top of your current location in the tree

git cherry-pick <COMMIT>

Grab a range of commits and put them on top of your current location in the tree

git cherry-pick <COMMIT BEFORE START>..<LAST COMMIT>

Deal with merge conflicts during a rebase

git mergetool

Move from your current commit in the tree to a different commit in the tree

git reset --hard <COMMIT>

Move from current commit to a different commit and stage all the difference between those commits

git reset --soft <COMMIT>

OH NO! I LOST A FILE! Did you commit? If not, your files are lost. If yes, then reflog to the rescue!

git reflog

Revert the changes you made in a commit as a new commit

git revert <COMMIT>

Time to get tricky

git version-number

A very useful notion resource for how the robotics guild uses git