Advanced · 7 min read
How Git works inside
Blobs, trees, commits and refs: once you see them, nothing in Git is magic anymore.
Four kinds of objects
A blob is a file's content. A tree is a folder (names → blobs and trees). A commit points to a tree, its parent(s), an author and a message. A tag points to a commit. Each one is identified by the hash of its content.
Safe
$ git cat-file -p HEAD$ git cat-file -p HEAD^{tree}
Branches are just files
A branch is a small file containing a commit hash. HEAD says which branch you're on. That's why creating a branch is instant.
Safe
$ cat .git/HEAD$ git rev-parse main
Why almost nothing is lost
Objects are never modified, only added. A reset or a deleted branch only moves or removes a name; the objects stay until garbage collection, and the reflog remembers where the names were.
Safe
$ git reflog$ git fsck --unreachable