Lesson 3: Editors & Version Control

Check in from last week

Is anyone having problems with package management?

Install the packages named git, vim, and emacs

What we'll discuss

• What's a text editor?
• Features of an editor
• Version control: Git!

How do you edit files?

No. Never, Ever edit code in Word/LibreOffice

• Autocorrect is your worst enemy
• Syntax highlighting is nice
• You are editing plain text, not 'documents', i.e. .doc, .rtf, etc

Then what should you use?

• Text editors

  • Command-line
  • available in your package manager

• For coding, an IDE can be helpful

Integrated Development Environments

• Entire toolchain in one place
• Usually graphical

Sysadmin tools

• Frequently work with remote machines over a ssh connection

  • xforwarding can sort of give you a GUI
  • Not all remote machines have a desktop environment

• Faster to edit file in place than transfer it down then back up

  • Frequent small changes when testing or debugging

• Broken machines often have only terminal via crash cart

Features of an editor

• Needs to be installed on your system
• Create files
• Move around within the file
• Add or delete text
• Easily automate tedious tasks

Text Editors

• ed -> Vi -> Vim
• Stallman -> lisp -> emacs

Avoid Pico/Nano, Notepad++, SublimeText

Emacs

But, along the way, I wrote a text editor, Emacs. The interesting idea about Emacs was that it had a programming language, and the user's editing commands would be written in that interpreted programming language, so that you could load new commands into your editor while you were editing. You could edit the programs you were using and then go on editing with them.

-- Richard Stallman, http://www.gnu.org/gnu/rms-lisp.html

Vim

• Available almost everywhere
• Lightweight
• Design decisions explained in http://docs.freebsd.org/44doc/usd/12.vi/paper.html
• Modal editor (command, insert, visual)

How to choose

• What can the people around you help with?

• Try both; choose one and get good at it

• Have a good answer when people ask why you made that choice

  • "Because it's familiar" is tolerated
  • "Because I was initially taught it" is common but accepted (honesty)
  • "Because $usecase" provokes argument but more respected
  • "Because I tried both and picked this one" is rare but good

• Your use case as a sysadmin or developer

Modes

How to tell?

-- INSERT --                                          144,1    36%
-- VISUAL --                                          144,77   36%

Commands

Moving Around

h move one character to the left.
j move down one line.
k move up one line.
l move one character to the right.
0 move to the beginning of the line.
$ move to the end of the line.
w move forward one word.
b move backward one word.
G move to the end of the file.
gg move to the beginning of the file.
. move to the last edit.

Configuration / customization

• .vimrc
• :set

Some sets of Vim plugins and configurations are available

• https://github.com/astrails/dotvim
• https://github.com/carlhuda/janus

Use them for research on what's available to improve dev productivity

Learning Resources

• $ vimtutor
• http://vim-adventures.com/

Regular expressions

You should know basic substitution:

:%s/foo/bar/g

On IRC, Hamper does rudimentary regex in the form s/foo/bar/ applying only to the most recent comment.

This is not shell globbing

Editor questions?

• Open an editor, find a cheat sheet, try to add some text
• Modify the text: "disemvowel" it

$ vim testvim.txt            $ emacs testemacs.txt
<i>                          Hello world!
Hello world!                 <esc>
<esc>                        <
:%s/[aeiou]//g               <alt + x>
:wq                          replace-regexp
                             [aeiou]
                             <enter>
                             <ctrl + x> <ctrl + s>
                             <ctrl + x> <ctrl + c>

Lesson 3: Intro to Git

Version Control is Hard

Image from XKCD

Why Bother?

Image from PhD Comics

Better Options: Version Control

• Commit = Snapshot of part of your project's state

• Centralized (SVN, CVS) vs. Decentralized (Git, hg)

• We'll look at Git today

  • Easier to learn other VCS from Git
  • Widely used in the open source world

Git

git

noun. Brit.informal. 1. an unpleasant or contemptible person.

Using Git Locally

# This initializes a git repo. Use `man git-init` for more info.
$ git init

# This puts <filename> into the staging area. It isn't committed yet.  Use
# `git diff` to see what changes aren't yet in staging.
$ git add <filename>

# This actually makes the commit. Use `git status` to see what's in staging
# but not yet committed. Use `git show` or `git log` to see recent commits.
$ git commit -m "I did a thing!"

• Undo things? the git book explains well
• Did I remember to commit that? $ git status
• What commits have I made lately? $ git log

More on commits

Your work goes from unstaged to staging area with git add.

$ git config --global user.name 'Your Name'
$ git config --global user.email you@somedomain.com

• Everything in staging gets wrapped up into an object that contains

  • changes
  • timestamp
  • author info
  • parent commit hash

• These live in .git/ in your project directory

• Commits go to other locations with git push

What Not To Do

image from http://arstechnica.com/security/2013/01/psa-dont-upload-your-important-passwords-to-github/

• Don't delete the .git files

• Redundant copies of same work

• "oops, undoing that" commits.

  • Use git commit --amend

• Don't wait too long between commits

  • Squashing them together later is easy

• Don't commit compiled/generated items

• Don't commit secrets...

Daily workflow

• Pull
• Work
• Add changes
• Commit
• Push

Larger projects have more complex workflows

Lesson 3: GitHub

• Manage permissions on repos
• Back up your work
• Social/gamification
• Amazing documentation: http://help.github.com

Let's Walk Through

• Creating an account

  • Gravatar
  • How to read a profile

• Creating SSH keys

  • ssh-keygen -t rsa

• Uploading your SSH key

• Creating a new repository

• Fork somebody else's repo

• Edit files online

• Submit a pull request

Help, Everythings's Broken!

Permission denied (publickey).
fatal: The remote end hung up unexpectedly

To git@github.com:edunham/slides.git
 ! [rejected]        master -> master (non-fast-forward)
error: failed to push some refs to 'git@github.com:edunham/slides.git'
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Merge the remote changes (e.g. 'git pull')
hint: before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

Learn More

• http://git-scm.com/book
• http://try.github.io/levels/1/challenges/1

Hands-On

• Fork the devopsbootcamp dotfiles repo
• Clone a copy of the repo to your VM and make a branch
• Make a commit with a helpful commit message and push to your fork

$ ssh-keygen -t rsa # make an SSH key and add it to your account
$ git clone <url from sidebar of your fork> # clone the repo
$ cd dotfiles # git commands only work in project directlry
$ git checkout -b <yourname> # -b creates branch
$ vim <filename>
    # 'i' to enter insert mode
    # <esc> to get back to command mode
    # :wq to save and quit
$ git add <filename>
$ git commit -m "please use a helpful commit message, not like this one"
$ git push