git-hero

From git-zero to

Michał Urbanek

Git as we know it

clone
branch
add
commit
pull
status

push
log
checkout
merge
blame
...

Environment

PS1='\[\e[0;33m\]\u\[\e[0m\]@\[\e[0;32m\]\h\[\e[0m\]:
     \[\e[0;34m\]\w\[\e[0;31m\]$(git_prompt)\[\e[0m\]\$ '

git_prompt ()
{
    if ! git rev-parse --git-dir > /dev/null 2>&1; then
        return 0
    fi

    git_branch=$(git branch 2>/dev/null| sed -n '/^\*/s/^\* //p')
    echo " [$git_branch]"
}

# git completion
source ~/.git-completion.bash

Aliases


  git config --global alias.co checkout
  git config --global alias.br branch
  git config --global alias.ci commit
  git config --global alias.st status
  git config --global alias.visual "!gitk"

no need to type long commands
shortcuts for most frequent commands
create commands that you think should exist
run external commands with !

Staging area

# add file.txt to staging area
git add file.txt

# display changes scheduled for committing
git diff --cached

# add only patch of given file
git add -p

Work in progress

# git stash with description MESSAGE
git stash save MESSAGE

# list all stashes
git stash list

# show diff from stash STASH
git stash show -p STASH

# apply and remove last stash
git stash pop

# apply and remove stash STASH
git stash pop STASH

# custom alias to actually make a commit
git save

alias.save !git add -A && git commit -m 'SAVEPOINT'

Debugging with git

# see commits with last changes file.txt in lines 5-10
git blame -L5,10 file.txt

# see commits with last changes in file.txt before commit <COMMIT-ID>
git blame COMMIT-ID -- file.txt

# get all commits which diff contained TEXT
git log -S"TEXT"

# start bisect between GOOD and BAD commits
git bisect start BAD GOOD

# mark commit as correct
git bisect good

# mark commit as invalid
git bisect bad

# run command "test.sh" automatically for each commit
git bisect run test.sh

Are git commits immutable?

Git model

A DAG of immutable commit objects where branches are named mutable pointers into it

git commit --amend

fix up the most recent commit
combine staged changes with previous commit
simply edit previous commit message

actually it completely replaces previous commit with a new one

merge vs rebase

they both solve the same problem
integrate changes from one branch to another
they just do it in very different ways

git merge

easier to understand
creates a new "merge" commit
non-destructive
easy to revert
log might be confusing


    git merge master feature

git rebase

moves entire "feature" branch to begin on the tip of the master branch
rewrites/simplifies project history
creates brand new commits for each commit in original branch


    git checkout feature
    git rebase master

git pull --rebase

by default pull performs merge
this way it will rather perform rebase
this behaviour can be set to default

rebase pros

much cleaner project history
no merge commits
perfectly linear history - no forks
easier to navigate with git bisect, git log, gitk

The dark side of rebase

loses context of workflow
potentially catastrophic for collaboration workflow

The golden rule of rebase

Is anyone else looking at this branch?
YES - take your hands off the keyboard. NOW!
NO - just do it!

Interactive rebase


    git checkout feature
    git rebase -i master

more powerful then automated rebase
offers full control over branche's history
clean up messy history before merge
like git commit --amend on steroids
split, reorder, remove, alter existing commits

Rule of thumb

use pull --rebase
DO rebase small local branches
do NOT rebase long living branches on which you collaborate with others
in such case it's better to do an explicit merge --no-ff

Trust this guy

People can (and probably should) rebase their private trees (their own work). That's a cleanup.

But never other peoples code. That's a "destroy history".

Linus Torvalds

Where did my commits go?

Reflog

The reflog is Git’s safety net. It records almost every change you make in your repository, regardless of whether you committed a snapshot or not.

 git reflog

Submodules

# add submodule from repository at <MODULE-URL>
git submodule add <MODULE-URL>

# see detailed submodule changes
git diff --submodule

# init submodule after clone
git submodule init

# populate submodule
git submodule update

# update submodule to newest version from submodules repo
git submodule update --remote

# update submodule and rebase local changes (if any)
git submodule update --remote --rebase

# push changes together with all local submodule commits
git push --recurse-submodules=on-demand

# useful aliases
git config alias.sdiff '!'"git diff && git submodule foreach 'git diff'"
git config alias.spush 'push --recurse-submodules=on-demand'
git config alias.supdate 'submodule update --remote --merge'

Cleaning up..

Command	Scope	Common use cases
git reset	Commit-level	Discard commits in a private branch or throw away uncommited changes
git reset	File-level	Unstage a file
git checkout	Commit-level	Switch between branches or inspect old snapshots
git checkout	File-level	Discard changes in the working directory
git revert	Commit-level	Undo commits in a public branch
git revert	File-level	(N/A)

git reset

git revert

References

https://git-scm.com/book/en/v2/Getting-Started-Git-Basics
https://git-scm.com/book/en/v2/Git-Tools-Submodules
https://www.atlassian.com/git/tutorials
http://git-scm.com/book/en/v2/Git-Branching-Rebasing
https://blog.sourcetreeapp.com/2012/08/21/merge-or-rebase/
http://nathanleclaire.com/blog/2014/09/14/dont-be-scared-of-git-rebase/
http://www.mail-archive.com/dri-devel@lists.sourceforge.net/msg39091.html
https://github.com/jakubnabrdalik/gitkurwa
http://haacked.com/archive/2014/07/28/github-flow-aliases/