git - beyond basic

but not too far though

This talk

• What's in a repo
• What are these things you speak of
• Some HOWTO

What's in a repo

Hands-on

• Initialise repository
• Look inside the `.git` directory
• Create some commits
• Create a branch
• Add a remote

Thesaurus

HEAD

• Reference to the currently checked-out commit
• Don't worry too much about it
• A repository thing
• Has nothing to do with the working directory or the staging area

• $ cat ./.git/HEAD

• As new commits are created, the reference is updated
• Analogy: cassette tape recorder head
• SO: What is the HEAD in git?

detached HEAD

• Not as bad as it sounds
• When you check out something other than a branch
• You wouldn't normally commit now
• If you do want to commit, create a branch first

X_X ohnoe X_X

Remote

• Remote repository
• Convention is that the main one is named `origin`
• Can have more
• Can be on the same machine
• Can be on a colleague's machine
• Yay distributed!

Fork

• Not an actual git concept
• Depends on the provider (e.g. GitHub)
• In GH it creates a remote copy of someone else's repo
• FOSS that you want to use, but needs some customisation

Tilda, caret

• Navigation relative to the ref
• Usual example HEAD~1 (or HEAD^)
• HEAD~1 = HEAD^ = the parent of HEAD
• HEAD~2 = HEAD^^ = the parent of the parent of HEAD
• Useful when rebasing
• Paul Boxley: Git caret and tilde
• Pro Git (2nd ed): Revision selection

States

1. Working tree (or directory)
2. Staging area (or index)
3. git repository (local)
4. Remote

• Pro Git: The three states
• NDP software: git cheatsheet

States

• Or working directory
• A place on the filesystem
• Where the repository has been cloned
• The state of the files checked-out and modified

Working tree

States

• Staging area
• Changes are marked for commit
• The next commit will add staged to the next state

Index

States

• Local repository
• ./.git directory
• ...

git repository

States

• Secret ninja place thingy
• NOT commits
• Only on the local repo
• Others don't see them

stash

Basic advanced commands

stash

• Not on the working tree
• Not on the index
• Not in the history

fetch

• Fetch refs (branches, tags) from remote
• Update your local from the remote
• Not destructive

reset

• Set HEAD to commit
• And a bunch of other things

$ git reset [--soft | --mixed | --hard] <commit>

--soft

• Leaves index and working tree untouched
• Ready to be committed

--mixed

• Resets index, but not the working tree
• Just like you created new files

--hard

• Resets index and working tree for the tracked files

checkout

• Switches to the branch
• Updates HEAD to point at that ref

$ git checkout <branch> | <commit>

• Undoes all the unstaged changes

$ git checkout -- .

status

• Differences between index and last commit (HEAD)

cherry-pick

• Copy a commit on a different branch
• Useful when only a subset of the changes is needed

rebase

• Re-creates commits on top of other ones
• Destructive action, so be careful!
• Never rebase things that have already been pushed

tread carefully

$ git rebase master topic

• Takes each commit from the `topic` branch
• Re-creates on top of the `master` branch

rebase --interactive

• Alter some successful commits
• Still a destructive action, so be careful!

tread carefully

$ git rebase --interactive HEAD~3

• Look at the last 3 commits before HEAD
• Edit commit message
• Edit actual changed code from a commit
• Remove a commit
• Move a commit's position

Some config things

alias

• Shorthand if you use the CLI
• `git st` for `git status`
• `git lg` for `git log --graph --pretty=...`

HOWTO

Undo things

• Remove the last commit
• Remove an older commit
• ... ?

Remove a commit

• How far back is it?
• Are those changes used later?
• Do you want it gone forever?
• Do you need the changes?
• Do you want to move it someplace else?
• So many cases, so many ways of doing it!

Remove a commit

• If it's the last commit on a branch
• Are those changes used later?
• Do you want it gone forever?
• Do you need the changes?
• Do you want to move it someplace else?
• So many cases, so many ways of doing it!

reset

$ git reset <mode> HEAD~1

Games and books

Interactive tutorials

• GitHub interactive tutorial - https://try.github.io/

• Codeschool course - https://www.codeschool.com/learn/git

• http://ndpsoftware.com/git-cheatsheet.html#loc=stash;

Reading

• Everyday git - https://git-scm.com/docs/giteveryday

• Pro Git (2nd ed) - https://git-scm.com/book/en/v2

Most important

• Practice, practice, practice