This Sugar adds three commands in the Actions→Convert/Strip menu to convert all the linebreaks in the frontmost document to either Unix, Windows, or Mac-style linebreaks. There is also an action to make your linebreaks lonely (strip all non-linebreak whitespace from empty lines).
Requires Espresso 2.1
The easiest way to install ConvertLinebreaks.sugar is directly from GitHub:
cd ~/Library/Application\ Support/Espresso/Sugars
git clone git://github.com/onecrayon/ConvertLinebreaks.sugar.git
Relaunch Espresso after installing the Sugar to gain access to its actions.
Copyright (c) 2011-2017 Ian Beck
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