Information Technology Reference
In-Depth Information
• When you commit the new revision goes to the current branch. The file
.git/HEAD
doesn't change. The SHA-1 of the newly created revision
will be stored in the
.git/refs/heads/branch-name
file. If the
branch was already stored in a packed format, the format is changed to
loose.
• When you create a new branch with
$ git branch branch-
name
a new file
.git/refs/heads/branch-name
is created and
it stores the SHA-1 of the revision passed as a parameter to the
$ git
branch
command or the current revision. The file
.git/HEAD
remains
unchanged. The format for a new branch is always loose.
• When you switch branches with the
$ git checkout branch-
name
command, all the files in
.git/refs/heads
remain unchanged.
The symbolic reference to the branch
branch-name
is stored in
.git/
HEAD
. It has the form
ref: refs/heads/branch-name
. The com-
mand resets the working directory to the state conforming to the latest
revision in
branch-name
branch. The command doesn't change the
format for storing a branch tip.
As you have learned in the Solution section of Recipe 5-1, both operations, creating
and switching to a new branch, can be achieved with one command:
$ git checkout -b new-branch existing-branch
This command creates a new branch named
new-branch
that points to the same
revision as an existing branch named
existing-branch
.
The
HEAD
plays a very special role in many git commands. Everywhere you need
the SHA-1 of the revision that you are currently working on, you can use
HEAD
in-
stead. Moreover,
HEAD
is usually a default value used for absent parameters. The com-
mands:
$ git reset --hard
$ git reset --hard HEAD
are identical. In a similar fashion, you can create a new branch with:
$ git branch new-name [REVISION]
