Git Tag

Lightweight Tags

We can create a tag to refer to a particular commit by running git tag with no arguments.

$ git tag stable-1 1b2e1d63ff

After that, we can use stable-1 to refer to the commit 1b2e1d63ff.

This creates a "lightweight" tag, basically a branch that never moves. If you would also like to include a comment with the tag, and possibly sign it cryptographically, then we can create a tag object instead.

Tag Objects

If one of -a, -s, or -u is passed, the command creates a tag object, and requires the tag message. Unless -m or -F is given, an editor is started for the user to type in the tag message.

When this happens, a new object is added to the Git object database and the tag ref points to that tag object, rather than the commit itself. The strength of this is that you can sign the tag, so you can verify that it is the correct commit later. You can create a tag object like this:

$ git tag -a stable-1 1b2e1d63ff

It is actually possible to tag any object, but tagging commit objects is the most common. (In the Linux kernel source, the first tag object references a tree, rather than a commit)

Signed Tags

If you have a GPG key setup, you can create signed tags fairly easily. First, you will probably want to setup your key id in your .git/config or ~.gitconfig file.

[user]
    signingkey = <gpg-key-id>

You can also set that with

$ git config (--global) user.signingkey <gpg-key-id>

Now you can create a signed tag simply by replacing the -a with a -s.

$ git tag -s stable-1 1b2e1d63ff

If you don't have your GPG key in your config file, you can accomplish the same thing this way:

$ git tag -u <gpg-key-id> stable-1 1b2e1d63ff