## `git cat-file <type> <object-id>`
Display the specified object, where <type> is one of commit, tree, blob, or tag.

## `git cat-file -t <object-id>`
Output the type of the specified object.

## `git ls-tree <tree-id>`
Display a pretty version of the specified tree object.

## `git gc`
Perform a garbage collection on the object database.

## `git update-index [--add] <file>`
Stage the specified file, using the optional --add flag to denote a new untracked file.

## `git write-tree`
Generate a tree from the index and store it in the object database. Returns the ID of the new tree object.

## `git commit-tree <tree-id> -p <parent-id>`
Create a new commit object from the given tree object and parent commit. Returns the ID of the new commit object.