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06 · Undoing things in Git

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Engineering Toolkit, lesson 6

Undoing things in Git

Match each mistake to the undo that fixes it without losing work.

"Commits and the staging area" and "Branches, merges and conflicts": the staging area, HEAD and HEAD~1.

Part 1. Before you commit: restore and stash

Most mistakes happen before anything is committed. You tried an idea in count.py and it made things worse, and you also edited the README, which you want to keep.

Throwing away one file's edits
$ git status --short
 M README.md
 M count.py
$ git diff count.py
diff --git a/count.py b/count.py
index 53b8476..1bbdd40 100644
--- a/count.py
+++ b/count.py
@@ -5,5 +5,5 @@ from collections import Counter
 text = open(sys.argv[1]).read().lower()
 words = re.findall(r"[a-z']+", text)
 print("words:", len(words))
-for word, n in Counter(words).most_common(3):
+for word, n in Counter(words).most_common(30):
     print(word, n)
$ git restore count.py
$ git status --short
 M README.md

Your turn

You run git restore count.py on a file holding an afternoon of edits you never staged or committed. Can you get the edits back?

Git can only bring back what it stored, and edits that were never added or committed were never stored. git restore replaces the file with the last committed version, with no question asked. If in doubt, git stash first: it saves the edits and cleans the folder in one step.

git restore --staged is the gentler one: it takes a file out of the next commit and leaves your edits alone. git stash sets all your changes aside, so you get a clean folder (to switch branch, or pull) without committing half-done work. git stash pop brings them back.

Unstaging, and stashing
$ git add README.md
$ git restore --staged README.md
$ git status --short
 M README.md
$ git stash
Saved working directory and index state WIP on main: a24cc41 Leave out environments, secrets and data
$ git status --short
$ git stash pop
On branch main
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
	modified:   README.md

no changes added to commit (use "git add" and/or "git commit -a")
Dropped refs/stash@{0} (a67a53ce222dad950e8b7350a26929c9d808c1c7)

Stash

A shelf for uncommitted changes. git stash saves them and cleans the working tree, git stash list shows what's on the shelf, and git stash pop puts the newest back.

Part 2. The last commit: amend and reset

Keep going with Pro

You've done the first part. Pro opens the rest of this lesson, and every other one.

Still to come
  1. The last commit: amend and reset
  2. Already shared: revert
  3. When a commit seems lost: the reflog
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Next lessonSetting up a Python projectA project anyone can install, run and test the same way anywhere. Start lesson 7

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