Git Exercises

# 1. Interactive rebase - clean up history before a PR
# Make a feature branch with messy commits
git switch -c feat/login
echo 'a' >> file.txt; git add . && git commit -m 'wip a'
echo 'b' >> file.txt; git add . && git commit -m 'wip b'
echo 'c' >> file.txt; git add . && git commit -m 'fixup typo'
echo 'd' >> file.txt; git add . && git commit -m 'wip c'

# Now interactive rebase to squash the wip commits into one clean commit
git rebase -i HEAD~4
# In the editor: change 'pick' to 'squash' for the wip lines, keep 'pick' on the first
# Save - then edit the combined message to be one clear summary

# Verify
git log --oneline -10


# 2. Bisect to find a regression
# Setup: a known good tag and a current broken HEAD
git bisect start
git bisect bad                   # current HEAD broken
git bisect good v1.0.0           # known good

# Git checks out a midpoint
# Run the test that fails
npm test
# If tests still fail:
git bisect bad
# If tests pass:
git bisect good

# Keep going until git says: <sha> is the first bad commit
git bisect reset
# You now have the exact commit. Fix it. Cherry-pick the fix into main.


# 3. Recover lost work via reflog
# Setup: simulate a bad reset
git switch main
git switch -c experiment
echo 'important' > work.txt; git add . && git commit -m 'important work'
git switch main
git branch -D experiment        # oops - branch deleted, work seemingly gone

# Recover
git reflog | head
# Output looks like:
# abc123 HEAD@{0}: checkout: moving from experiment to main
# def456 HEAD@{1}: commit: important work
# ...

# Restore by branching from the commit
git switch -c experiment-recovered def456
git log -1
cat work.txt    # back

# Stretch
# - Set rerere.enabled and rebase the same branch twice; the second time should auto-resolve
# - Use git worktree to do all three exercises in parallel without losing context

# Fill in the blank.
git ____ -m 'fix typo'