Tags

Another interesting concept in git are commit pointers,
in git these are called tags

A tag identifies a specific commit with a meaningful name, replacing the complicated hash

What are they for?

Tags are used to identify a commit as a significant one

e.g. tags could be used to identify the commit of a specific release of a program

How can we create a tag?

git tag <tag_name> [<commit_hash>]

The command tag requires a name for the tag and optionally the hash of the commit which has to be tagged (If no hash is provided the "last" commit will be tagged)

Tag a specific commit

git tag v1.2.0 be4f621

A pointer is added to the commit with the specified name

How can we get the list of tags?

Simply using

git tag

v1.0
v1.1.1
v1.2.0
(END)

tag without parameters returns the list of the repository tags

History as commit pointers

As we said earlier each commit has a pointer to its parent, so we can see the entire history of a git repo like a collection of commits and commit pointers

Branches as commit pointers

We used an intuitive meaning of branch for simplicity, but in the real git the branches are really similar to commit pointers

In particular branch is a pointer to the last commit of the "intuitive branch"

Branches are tags
(more or less)

Which commit is a new one attached to?

The answer is "the commit pointed to by HEAD"

The special tag HEAD

HEAD is a special tag pointing the current working branch
in an ordinary situation

Which operations (implicitly) move HEAD?

• Change branch (switch)
  move HEAD to a branch
• Create a commit (commit)
  move HEAD to the new commit

What if we want to move HEAD
to a specific commit?

To do this we can use the command checkout with the hash of the commit we want move HEAD to

git checkout <commit_hash>