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Creating Commits

Most steps of this tutorial are done by typing shell commands. The grey boxes contain the commands you should enter, preceded by a $ symbol, together with their output. While you may copy & paste these commands, some of them may require modifications to adapt them to your own projects.

1. Read the Git for Computer Scientists introduction (skip this if you are already familiar with Git). 
2. For Linux, Git is available in its own package. Windows users can install msysGit. For Mac OSX, Git is available as part of Xcode; if you cannot install that, use Git for OSX.

3. Configure your name and email address (will be included in all commits you create):

   No Format
   $ git config --global --add user.name "Your Name" $ git config --global --add user.email "<login>@informatik.uni-kiel.de"

4. Create a local repository for the "Turing Project":

   No Format
   $ mkdir turing $ cd turing $ git init Initialized empty Git repository in ~/turing/.git/

   The .git subdirectory contains all history and metadata of the repository. You should not modify it. The turing directory contains the working copy, that is the currently checked-out snapshot. You work by modifying your working copy and committing the modifications to the repository (contained in .git).

5. Add and commit some content: copy notes.txt to your turing directory.

   No Format
   $ git add notes.txt $ git commit -m "wrote some first notes" [master (root-commit) 2e73b34] wrote some first notes 1 files changed, 5 insertions(+), 0 deletions(-) create mode 100644 notes.txt

   The file is now stored in the local history of your repository.

6. Edit notes.txt:
   
   1. Replace "fixed" with "infinite" in line 1.
   2. Replace "... (TODO)" with "a finite state machine" in line 4.

7. View the status of your current working copy:

   No Format
   $ git status # On branch master # Changed but not updated: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: notes.txt # no changes added to commit (use "git add" and/or "git commit -a")

8. Mark the modified file to include it in the next commit, then view the status again and compare with the previous output:

   No Format
   $ git add notes.txt $ git status # On branch master # Changes to be committed: # (use "git reset HEAD <file>..." to unstage) # # modified: notes.txt #

9. Commit the modified content to your local repository and view the status:

   No Format
   $ git commit -m "modified tape length, found a controller for tape head" [master 52e2d49] modified tape length, found a controller for tape head 1 files changed, 2 insertions(+), 2 deletions(-) $ git status # On branch master nothing to commit (working directory clean)

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Note that each commit is identified by a looong hash value, but it is possible to use only a prefix when referencing them (if the prefix is not ambiguous): the example above uses 52e2d49 to identify the second commit. The commit hashes in your repository will be different from those seen in this tutorial, because the name of the author and the exact time of committing is also considered in the hash calculation. Also try the command gitk to get an overview of your commits (a better alternative available for MacOS Mac OSX is GitX).

Branching and Merging

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