Git, and why version control exists
By the end of today you can explain what a commit actually is, why branching is cheap, and what a merge conflict physically represents, rather than memorising commands you do not understand.
YesterdayOn Day 9 you learned to isolate dependencies so a project is reproducible. Git does the same for the code itself, across time.
TomorrowTomorrow you use all of this to read a real codebase written by somebody else.
Why this matters
Git is the substrate every professional codebase sits on. People fear it because they learned commands instead of the model, and the model is genuinely simple once someone draws it.
- Commits
- Branches
- Merges and conflicts
- Remotes
Learn it
75 minCopy this into Claude or ChatGPT. It quizzes you before it explains anything, which is deliberate. The resources under it are how you check what it told you.
Today's Master Prompt
Free · sign inA prompt written for this day alone: your level, the exact scope, what to leave out, and an instruction to quiz you before it explains anything. Paste it into Claude or ChatGPT and it teaches you today's material.
Check it against something that is not a model
An assistant can be fluent and wrong, and on a topic you met today you will not catch it. These cover the same ground and were made by people who do this for a living, so they are what you hold the explanation up against. They are other people's work and we only link to them, so judge them for yourself.
6 hand-picked resources
Free · sign inVideos, official docs and articles covering the same ground, each opened and annotated by hand. They are what you check the assistant against on a day you cannot yet catch it being wrong.
Build it
45 minIn a scratch repository, create a branch, make two commits on it, switch back to main, make a conflicting change to the same lines, then merge and resolve the conflict by hand. Run git log --graph --oneline before and after each step and watch the shape change.
Recall it
20 minAnswer out loud, reveal, then mark honestly whether you had it. That score is the only thing on this page you do not get to choose.
4 recall questions
Free · sign inQuestions you answer from memory, then grade yourself against the real answer. The score is carried into the mastery rating below it, so an honest miss cannot quietly become a tick.
Rate it
Completion and mastery are tracked separately. Be honest, because an inflated rating only means the concept resurfaces sooner.
Mastery tracking
Free · sign inRate yourself against five named criteria per concept. Completion and mastery are tracked separately, and anything you rate shakily comes back automatically on a spaced schedule.
Recap
- 01A commit is a snapshot with a parent pointer, not a diff
- 02A branch is a movable pointer, which is why branching is free
- 03A conflict is git refusing to guess between two edits to the same lines
- 04Adding to history is safe; rewriting it after pushing is not
Your progress
Free · sign inMark days complete, pick up where you left off across devices, and watch completion and mastery diverge. Free, and the account exists only so ninety days of work cannot vanish with a cleared browser.