Web Programming @ MIPT

Git crash course

Web Programming @ MIPT, 2015-2016

What is VCS?

VCS stands for Version Control System
Configuration Management ⊃ Software Configuration Management ⊃ Version Control
VCS is used for:
- software development
- book writing (e.g., Open Math Book)
- design creation (less typical)

VCS terminology

Commits
Branches
Merges
Tags
History (log)
Centralized operation
- Locking
Distributed operation
- Pool and push
- Remotes

Typical smell of bad development (1)

What are the drawbacks?

Typical smell of bad development (1)

What are the drawbacks?

No way I will collaborate with others. Grab my archive and don't complain.

Typical smell of bad development (1)

What are the drawbacks?

No way I will collaborate with others. Grab my archive and don't complain.
Diffs? What diffs?

Typical smell of bad development (1)

What are the drawbacks?

No way I will collaborate with others. Grab my archive and don't complain.
Diffs? What diffs?
Merging branches? They are for losers!

Typical smell of bad development (1)

What are the drawbacks?

No way I will collaborate with others. Grab my archive and don't complain.
Diffs? What diffs?
Merging branches? They are for losers!
Making releases is simple. Just edit config files A and B, remove C, D and F directory, revise G to exclude my local modifications. Oh, and fix H to print the current version, of course.

Typical smell of bad development (1)

What are the drawbacks?

No way I will collaborate with others. Grab my archive and don't complain.
Diffs? What diffs?
Merging branches? They are for losers!
Making releases is simple. Just edit config files A and B, remove C, D and F directory, revise G to exclude my local modifications. Oh, and fix H to print the current version, of course.
My site has no bugs so there is nothing to search for in history.

Typical smell of bad development (2)

What are the drawbacks?

Typical smell of bad development (2)

What are the drawbacks?

I changed this file the last, so your changes disappeared.

Typical smell of bad development (2)

What are the drawbacks?

I changed this file the last, so your changes disappeared.
Diffs? That stupid question again!

Typical smell of bad development (2)

What are the drawbacks?

I changed this file the last, so your changes disappeared.
Diffs? That stupid question again!
Branching is impossible. Forget about merging.

Typical smell of bad development (2)

What are the drawbacks?

I changed this file the last, so your changes disappeared.
Diffs? That stupid question again!
Branching is impossible. Forget about merging.
Versioning is impossible.

Typical smell of bad development (2)

What are the drawbacks?

I changed this file the last, so your changes disappeared.
Diffs? That stupid question again!
Branching is impossible. Forget about merging.
Versioning is impossible.
Hard to use on windowless servers.

Always use VCS...

even if the project is small
even if you work alone
even if you are tired
even if aliens threaten your family

Existing VCS

Git - most popular
CVS, SVN - watch why they suck are bad
Bazaar, Mercurial - powerful, but unpopular
Perforce - in many cases, corporate standard (unfortunately)

Git history

Appeared in 2005 to solve Linux Kernel troubles
Original author was Linus Torvalds
Attracted popularity thanks to the launch of GitHub in 2008
21.1 million repositories in 2015

Main features of Git

Distributed
Fast (originally written in C) - scales to huge projects
Powerful and cheap branching
Durability and robustness
Simplicity of internal design (but not for the end user, unfortunately)

The Book

Pro Git (en), Pro Git (ru)
Two major versions, the latest is the second (Google still suggests the first!)
CC BY-NC-SA 3.0 license (open and free)
The source is maintained on GitHub
Screw the book, I want to practice at once

Getting Git

Ubuntu: sudo apt-get install git
MacOSX: brew install git
Windows: use GitHub for Windows
DO NOT USE GUI

Git basics: getting a repository

git init to initialize an empty repo
git clone to fetch an existing one

Examples:

				git init .
				git clone git@github.com:vmarkovtsev/mipt_web_2015.git mipt

Internal files are stored inside .git directory in the repo's root

Git basics: 4 areas

Git basics: status and history

git status - show what's going on
git log - show what happened before on the current branch
git reflog - show the last N repository states
Perhaps, these are the only commands where GUI can do better
GUI: gitk, qgit, SourceTree, [SmartGit, Tower], etc.

Git basics: add

git add [-p] - adds untracked and modified files to staging area
git add - mark conflict as resolved
git diff - show the difference between HEAD and modified (but not staged!)
git diff --staged - show the difference between HEAD and staged
git reset [-p] - remove the file from staging to modified or untracked
git checkout -f - restore deleted file, revert changes

Git basics: rm and mv

git rm - removes the file from Git and from the file system
git rm --cached - removes the file from Git but leaves it in the file system
git mv - move file

Git basics: commit

git commit [-m] - make the commit from staged
git commit --amend - meld staged into the previous commit (HEAD)
git rebase -i HEAD^^^ - change last 3 commits sequentially
This is usually when you are asked for user name and email for the first time

Git basics: remotes

git remote -v - view external repositories
git remote add - add external repository
git remote rm - remove external repository
git fetch - synchronize remote branches with local mirrors
Default remote is "origin"

Git basics: pull and push

git pull --rebase - take off local commits, apply remote's and finally return local
git pull - merge local branch with remote counterpart
git push <remote name> <branch name> - update remote branch

Git basics: branches

Default is "master"
git branch - set new branch to point to HEAD, but do not switch to it
git checkout -b - set new branch to point to HEAD, and switch to it
git checkout - switch to existing branch
git branch -d/-D - delete branch (local)
git push <remote name> :<name> - delete branch (remote)
Git Koans
Interactive tutorial

Git basics: merge and rebase

git merge [--squash] - merge with other branch
git rebase - rebase against other branch
git cherry-pick - take commit(s), duplicating history
git mergetool - resolve conflicts

GitHub demo

Git branching models

git flow
Only "master"/"develop" and "production"/"master" - works only with pre-commit code review, e.g. Gerrit
See also Atlassian tutorial

Git basics: stashing

git stash - take the snapshot of modified and staged, then do git reset --hard
git stash pop - recover the modified and staged
git stash list - view LIFO

Git basics: tagging

git tag - mark HEAD with a label
git pull --tags - fetch tags, too
git push --tags - push with tags

Git basics: patches

git format-patch <commit> - create patch files from each commit after <commit>
The output looks very much like git diff
git apply - apply patch

Git submodules

git submodule add <where> <path> - register new submodule
git submodule update --init [--recursive] - pulls all submodules and detaches HEADs of each
Use submodules only if you really have to

Git maintenance

git fsck - check internal integrity
git gc - garbage collect objects
BFG Repo-Cleaner

Next steps

Register on GitHub
Create the repository for your future project
Pass interactive git tutorials: 1, 2, 3, 4
Download cheatsheet
Continue to HTML5 (semantics)