Keep tracks of defaults write and Useful defaults write commands

In .bashrc, create the line

PROMPT_COMMAND='echo "$(history 1 | grep "defaults")" | sed '/^$/d' >> ~/Documents/defaults.txt'

To undo the changes, use 'defaults delete'. For example,
defaults write xxx - bool false
defaults delete xxx

- Change to transparent dock in Mavericks

defaults write com.apple.dock hide-mirror -bool true;killall Dock

- Change screen capture file format

defaults write com.apple.screencapture type jpg; killall SystemUIServer
defaults write com.apple.screencapture disable-shadow -bool false

- Add 'Save as' back to applications

defaults write com.apple.iWork.Keynote ApplePersistence - bool no

defaults write com.apple.TextEdit ApplePersistence - bool no

defaults write com.apple.Preview ApplePersistence - bool no