Handy Git tricks

git_tricks.sh

## discard modifications in a directory
git checkout -- Gemfile # reset specified path 
git checkout -- lib bin # also works with multiple arguments

## Undo local commits
git reset HEAD~2        # undo last two commits, keep changes
git reset --hard HEAD~2 # undo last two commits, discard changes  

## Remove a file from the repo, but keep it in the filesystem
git reset filename          # or git remove --cached filename
echo filename >> .gitingore # add it to .gitignore to avoid re-adding it

## Edit a commit message
git commit --amend                  # start $EDITOR to edit the message
git commit --amend -m "New message" # set the new message directly

## Add a forgotten file to the last commit
git add forgotten_file 
git commit --amend

## Clean up local commits before pushing
## Good for squashing 
git rebase --interactive 
# if you didn't specify any tracking information for this branch 
# you will have to add upstream and remote branch information: 
git rebase --interactive origin branch

## Revert pushed commits
git revert c761f5c              # reverts the commit with the specified id
git revert HEAD^                # reverts the second to last commit
git revert develop~4..develop~2 # reverts a whole range of commits

# undo the last commit, but don't create a revert commit 
git revert -n HEAD

## Completely remove a sensitive file (secrets.txt) from a public repo
## CAUTION: this re-writes the history all branches and tags, and can be disruptive.
git filter-branch --force --index-filter \
  'git rm --cached --ignore-unmatch secrets.txt' \
  --prune-empty --tag-name-filter cat -- --all