Question

What is git is-tree?

Answer 1

‘git is-tree’ signifies a tree object comprising the mode and the name of all items along with the SHA-1 value of the blob or the tree.

Answer 2

The Work­ing Tree in Git is a direc­to­ry (and its files and sub­di­rec­to­ries) on your file sys­tem that is asso­ci­at­ed with a repository. 

It’s full of the files you edit, where you add new files, and from which you remove unneed­ed files. Any changes to the Work­ing Tree are not­ed by the Index (see below), and show up as mod­i­fied files.

When you open the files for a project that is being man­aged as a Git repos­i­to­ry then you are access the Work­ing Tree.

Tags and HEAD

Tags and HEAD are the same thing as branches: Pointers to a commit. The difference is that tags never move, even when you commit -- they're fixed pointers to a single commit object in the tree.

HEAD, on the other hand, moves a lot. When you commit, it moves to point to that new commit object. When you git checkout another branch, it moves to point to the same place that branch is pointing (...mostly). You can even git checkout individual commits or tags, and your HEAD will point to those commits.