Stage and commit

The staging area lets you choose exactly what goes into each commit. Small commits about one thing are the habit that makes everything else in git easy.

Goal#

Read what changed, stage only some of it, and make two commits that each say one thing.

See what changed#

shell

git status            # which files changed
git diff              # the lines that changed, not yet staged
git diff --staged     # the lines that will go into the next commit

git add puts a file's current state on the stage. git commit saves exactly what is on the stage, nothing else. Change a file after staging it, and the commit gets the staged version: git status shows the file twice to warn you.

One commit, one idea#

A good commit is about one thing, and its message says why:

Message	Why it is good or bad
`update stuff`	says nothing
`Add tuna to the dinner menu`	one thing, in the imperative
`Fix nap times shown in the wrong zone`	says what was wrong, so a reviewer knows

This matters even more when an AI agent writes the code. Small commits are small diffs, and small diffs are what humans actually review.

Quest 02#

shell

quest start 2

Three files changed while HEAD was napping: naps.txt is about sleep, and menu.txt and toys.txt are about her new things. Make one commit for each idea:

commit naps.txt on its own
commit menu.txt and toys.txt together

Use git status, git add with file names, and git diff --staged before each commit. Then quest check.

Check it works#

git log --oneline shows your two new commits, each with a clear message.
quest check passes.

Exercise#

Change two lines in one file, far apart. Stage only one of them with git add -p (patch mode): answer y for the hunk you want and n for the other. Commit, then look at git status. The other change is still waiting.

More to try

git commit with no -m opens your editor for a longer message: a short first line, a blank line, then the why. Try it.
git log --stat shows which files each commit touched.

Quest 02

quest start 2
# ...fix it with real git...
quest check

Mark it done once quest check shows every line as PASS. Your progress stays in this browser.