Outline

• Bonus Inteview Question
• Version Control Systems
• Quiz
• Git

Bonus Interview Question

Purpose: Second chance at course learning outcomes from the midterm. Successful completion of bonus is worth half back for the points you lost on the midterm.

Due Date: Dec 12 before office hours over.

Description: Write a PHP program, present it to me, and answer questions about it during my office hours on my white board without notes. Your program should read into an array of lines, $lines, every kth row of file foo.txt in the current working directory. Here k should be a define to the 5th digit of your student id. Your program should take the $_REQUEST['foo'] variable and check if it is a string. If it is a string, it should insert the tuples ($line, $_REQUEST['foo']) for each $line in $lines into a mysql table FOO using a prepared statement.

Version Control Systems

• A version control system solves the problem of how many people can work on the same code base at the same time.
• It also serves as a proof of work which can be used in legal cases -- the history of versions proving the code did not materialize out of nowhere.
• The oldest version control system is Source Code Control System developed at Bell Labs in 1972.
• It was subsequently supplanted in popularity by RCS (Revision Control System) which in turn was supplanted by CVS (Concurrent Version System).
• Nowadays, there are many different versions control systems on the on the market.
• There are traditional central repository systems: CVS, Subversion (open source); BitKeeper, Perforce, ClearCase ( proprietary)
• There are also distributed version control systems: Bazaar, git, Mercurial.
• Here is a round-up of the different features of these systems http://en.wikipedia.org/wiki/Comparison_of_revision_control_software
• Today, we are going to look at the git version control system as one means to manage our own projects. So we are going to be looking at a distributed VCS
• We will then talk about GitHub which is a web-site for hosting git repository. This central web-site and its features will give us a little bit of the flavor of how centralized repos work.
• According to Eclipse Community Survey 2014, at least among Eclipse users, Git and GitHub together have a 43% market share (33% Git/10% GitHub). (As of March, 2016, this was the most recent version of this survey I could find.)
• For comparison, Subversion is the next most popular version control system with a 31% share.

Git

• Git has been around since 2005, and was originally developed by Linus Torvalds, the creator of Linux.
• Git has a nice website for publicly hosting git repositories known as GitHub. Repositories on this sites get their own issue tracker (with rss feed) and wiki.
• To begin to set up a git repository move to where you would like to have your repository and type:

  git init name_of_git_repository.
  

• If you cd into this directory and do an ls -a to see hidden files, you will see a .git folder.
• The .git folder keeps a complete copy of all prior commits down for this repository.
• If you want to let someone to get a copy of your repository, you copy the repository folder on to a usb key (a key without Stuxnet please), give it to the person you want to have the repository.
• The person that wants to get your repository, might have an existing repository that they want to get your stuff into or might be starting from scratch. They issue a commands like:

  git clone path_to_clone_from to_folder #from scratch case
  git pull path_to_from_repos branch_name_you_want_to_pull_into #existing case
  git checkout branch #makes branch the current branch in the repository you are working on
  

• Notice sharing can be done locally without the need for a central repository, you can zip your git folders and e-mail, git even has its own e-mail commands.
• To see information about git commands, you can type 'git help', or 'git help command'

Quiz

Which of the following statements is true?

1. The PRG design pattern is used only when data is "get'd" from a form.
2. To declare a new namespace, the module keyword is used.
3. You cannot instantiate traits in PHP.

Quiz

Which of the following statements is true?

1. To declare a new namespace, the using keyword is used.
2. You can instantiate traits in PHP.
3. The PRG design pattern is supposed to keep the back button working when data is posted from a form.

Example Creating a Repository

mkdir myrepos
cd myrepos
git init
git add .
echo "hi there" > test.txt
git add test.txt
git commit -a -m "Initial commit"
cd ..
git clone file:///Users/cpollett/myrepos myrepos2
cd myrepos2 # now start editing myrepos2
echo "test2" > test2.txt
git add test2.txt
git commit -a -m "Made some changes"
cd ../myrepos #now want to get changes back in myrepos
git pull file:///Users/cpollett/myrepos2 master

git pull

Creating a WebDav repository

• If you want to have a workflow more like svn with a central repository you can configure a WebDAV directory in Apache on a server for git:

  <Location /git/myrepos.git>
  DAV on
  AuthType Basic
  AuthName "My site"
  AuthUserFile /etc/apache2/myrepos.passwd
  <LimitExcept GET HEAD PROPFIND OPTIONS REPORT >
  Require valid-user
  </LimitExcept>
  </Location>
  

• When you initialize your repository, you do the following commands:

  mkdir myrepos.git
  cd myrepos.git
  git init --bare
  git update-server-info
  

• You need to change the permissions and ownerships so the web server can access this folder, if _www was the user and group of the webserver then we could do:

  sudo chown -R _www .
  sudo chgrp -R _www .
  

• Finally, you would need to restart the webserver:

  sudo httpd -k stop
  sudo httpd -k start
  

Configuring your Repository

• To find out how our repository is set-up without trying to understand the contents of our .git folder, we can use the git config command:

  git config -l #lists current config settings.
  git config setting_name new_value #changes a setting
  

• Git will take a stab at figuring out who you are, but you will probably want to adjust the settings user.name and user.email to properly identify yourself when you commit changes:

  git config --global user.name "Your Name Comes Here"
  git config --global user.email you@yourdomain.example.com
  

• You might also want to use git config to configure an upload url:

  git config remote.upload.url http://myserver/git/myrepos.git
  

• Continuing the example of the last slide, we could populate the blank server's repository with stuff we make via:

  cd myrepos
  git init
  git add .
  git commit -m "setting up initial repository"
  git push upload master
  

  This might ask for password info. If you like you can configure a ~/.netrc file to save this info. This is a file on *nix systems with the following lines:

  machine [servername]
  login [username]
  password [password]
  

  where you replace what's in brackets with the relevant info.

Adding, Moving Files

• git doesn't manage files unless you tell git about them:

  git add file_or_folder 
  #folders added recursively, 
  #.gitignore can be used to list files you don't want added or managed.
  git clean #gets rid of files git doesn't know about
  git rm file  #removes the file from the repository, with -f deletes from filesystem
  git mv loc1 loc2 #moves file from loc1 to loc2
  git checkout [rev] file #gets the [rev] version of the file into the current branch
  #-f overwrites uncommitted changes.
  # Checkout master to go back to the most recent revision
  

• Git revision numbers are super-unmeaningful 20 byte SHA-1 hashes. Fortunately, you only need to use prefixes of a given hash number which are enough to uniquely identify a given branch.