Curriculum

A file's name in git is the hash of what is inside it.

A commit is a snapshot of everything, not a list of changes.

Forty bytes in a file. That is the entire feature.

The tree between your files and your history.

Two very different undos that people reach for interchangeably.

Replacing the last commit rather than editing it.

Reset's three modes are three different commands sharing a name.

A name that does not move.

Create and switch, in the modern spelling.

Two outcomes that look the same and are not.

Not an error. A question git cannot answer for you.

New commits with the same changes, on a different base.

Copying one change, and undoing one safely.

The one command that really does destroy something.

`origin/main` is not the remote. It is your memory of it.

What it costs somebody else, and the flag that checks first.

Twenty commits, five tests.

Your agent ran `reset --hard`. The commits are still there.

Deleting a branch removes a name, not the work.

An agent stopped halfway. The repository is not broken.

Deleting it in a new commit leaves it in every earlier one.

Garbage collection is real, and it is the end of the line.