• Getting Started with Git

We are going to make some changes to our earlier tolower program to make it more of a general-purpos character transliterator. Since we know what we have works, we would like a way to save that state and keep track of any subsequent changes. We will use git for that purpose.

Configure git

This is just a one-time step (repeated for each separate machine you plan to use git on). Follow the First-Time Git Setup instructions at least through the Your Identity section. You may chose to follow the next step, “Your Editor” if you would like to use a different editor to write commit messages other than the default (vim, unless you have your EDITOR environment variable set to something different).

Initialize a new repo

I am going to name my new git project motr, for “My Own tr” in reference to the Unix tr command. All this means is that the name of the new directory that git initilizes will be named motr. The name isn’t used anywhere else in the git configuration, so you can easily rename the directory later if you need to.

$ git init motr

You should now have a new sub directory named motr, run ls to confirm and then change into your new directory.

$ cd motr

If you run ls, you will see there are no output, but if you run ls -a you should see a directory named .git

$ ls -a
.  ..  .git

This is where git will store all of its information about the content you ask it to track. Typically you should avoid modifying any files in the .git directory manually, let git do this for you. But it is helpful to be reminded that like most Unix-inspired utilities, git stores its configuration and settings in a plain text format that you can view and edit with any text editor, if you need to.

Copy the original tolower.c source file

Since I want to start with what I had done in tolower.c I will copy that file into my new repository and rename it motr.c

$ cp ../tolower/tolower.c ./motr.c

you may have to adjust the source path ../tolower/tolower.c if your directory structure isn’t the same as mine. The .. in the path means the parent directory. If my current working directory is ~/ece2524/motr then ../tolower would refer to a directory at ~/ece2524/tolower.

Tell git to track changes

git does not automatically track files in a git-managed directory. This is because you will often have files in a git-managed directory that you do not want to track, so git expects you to explicity tell it which files it should track.

$ git add motr.c

we have just told git to add the motr.c file to the staging area. This means that it will be added to the git repository on the next commit. You can run git status at any time to get a summary of what files are staged for commit.

$ git status
# On branch master
#
# Initial commit
#
# Changes to be committed:
#   (use "git rm --cached <file>..." to unstage)
#
#       new file:   motr.c
#

Notice that git will often provide helpful hints in its output about how to correct potential mistakes. For instance, if you hadn’t intended to add motr.c to the staging area git tells you you can use the command git rm --cached <file> to unstage a file.

Make the first commit

$ git commit -m "Initial Commit"

Using the -m option will cause git to commit the changes using the message you supply after the -m option. To encourage detailed commit messages it is recommended to only use this short cut for the initial commit of a repository. Without the -m, git will open your default editor for you to write in a commit message. The convention is to follow the following format:

A short, descriptive title in the present tense

A more detailed paragraph. Keep both the title
and lines in the paragraph at 72 characters or
fewer.