creator after all.) Git keeps track of three main
structures, or trees (see Figure 2-8):
Local workspace: This is where you store source code files, binaries,
images, documentation, and whatever else you need.
Staging area: This is an intermediary storage area for items to be
synchronized (changes and new items).
Head, or local repository: This is where you store all committed
items.Figure 2-8 Git Tree Structure
Another very important concept with Git is the file
lifecycle. Each file that you add to your working directory
has a status attributed to it. This status determines how
Git handles the file. Figure 2-9 shows the Git file status
lifecycle, which includes the following statuses:
Untracked: When you first create a file in a directory that Git is
managing, it is given an untracked status. Git sees this file but does not
perform any type of version control operations on it. For all intents and
purposes, the file is invisible to the rest of the world. Some files, such as
those containing settings or passwords or temporary files, may be
stored in the working directory, but you may not want to include them
in version control. If you want Git to start tracking a file, you have to
explicitly tell it to do so with the git add command; once you do this,
the status of the file changes to tracked.
Unmodified: A tracked file in Git is included as part of the repository,
and changes are watched. This status means Git is watching for any file
changes that are made, but it doesn’t see any yet.
Modified: Whenever you add some code or make a change to the file,
Git changes the status of the file to modified. Modified status is where
Git sees that you are working on the file but you are not finished. You
have to tell Git that you are ready to add a changed (modified) file to
the index or staging area by issuing the git add command again.
Staged: Once a changed file is added to the index, Git needs to be able
to bundle up your changes and update the local repository. This process
is called staging and is accomplished through git commit. At this
point, your file status is moved back to the tracked status, and it stays
there until you make changes to the file in the future and kick off the
whole process once again.