git survival tips: how to undo and recover from your mistakes

Git Survival Tips

Tobias Güntherwww.git-tower.com

How to Undo & Recover from Your Mistakes

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Making changes in a complex software project

Undoing Local Changes

Undoing Local Changes

$ git checkout HEAD <filename> $ git reset --hard HEAD

Discarding uncommitted local changes cannot be undone!

Undoing Committed Changes

fix a typo in your last commitrevert a commit

in the middle restore the project at an earlier version

Amending Your Last Commit

Mistyped the commit message…

…and/or forgot to add a change.

Reverting Commits

Modifies “index.html” in the “opposite” way:(old) <div>About</div>(new) <div>About This Project</div>

Modified “index.html”:(old) <div>About This Project</div>(new) <div>About</div>

Reverting Commit

“git revert” creates a new commit (C4) thatreverts the effects of a specified commit (C2).

Resetting HEAD (aka “Rollback”)

master HEAD

master HEAD

Before reset

After reset

“git reset” sets your HEAD pointer (and thereby also your working copy) to an older revision. Commits that came after

this revision appear to be undone.

Undoing Committed Changes

$ git add forgotten_change.txt $ git commit --amend -m “Correct message”

$ git revert e81fc22

$ git reset --hard e81fc22

Recovering “Lost” Commits

master HEAD

master HEAD1. You think you want to reset.

2. You reset.

3. You notice it was a bad idea.

4. You panic.

— An Example —

Recovering “Lost” Commitsgit reflog a journal that logs every

movement of the HEAD pointer

Dealing with Merge ConflictsOMG! Help!

Dealing with Merge Conflicts

don’t panic!1. Git deals with most of the stuff.2. You only ever handicap yourself (not your team).3. You can always undo and start fresh.

— You Cannot Break Anything —

Dealing with Merge Conflicts— How a Conflict Happens —

Modifies line 16 in “about.html”:(old) <div>About</div>(new) <div>About Us</div>

Modifies the same line in in the same file:(old) <div>About</div>(new) <div>About Tower</div>

contact-form

master HEAD

merge conflict

Dealing with Merge Conflicts— What a Conflict Really Is —

1.Two contradictory versions(“A” and “B”) of a file.

2.…just funny letters in atext file.

Dealing with Merge Conflicts

Who made the changes?When?On which branches?In which commits?…

— Understanding What Happened —

Dealing with Merge Conflicts— Solving a Conflict —

(a) Use your editor / IDE to modify the file by hand.

(b) Use a Merge Tool.

(c) Use Tower / Git in easy cases.

= deciding, how it should finally look

Dealing with Merge Conflicts— Wrapping Up —

1. Save2. Stage / Add3. Commit = mark as resolved

(might already be done by external tool)

Get in Touch!

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