XDT Transformation tool is a command tool based on XDT (web.config) transform engine, which allows you to run XDT transformation on any XML files.
Scott Guthrie: "In most real-world deployment scenarios, the web.config file you use for development is different than the one you use for production deployment. Typically you want to change environment settings like database connection-strings, making sure debug is turned off, and enabling custom errors so that end-users (and hackers) don’t see the internals of your application."
If you want to know more about XDT Transformation Syntax, follow this link Deployment Web Application Project.
Using chocolatey.org.
choco install ctt
Also, you can download from latest Build.
ctt source:"Web.config" transform:"Web.Release.config" destination:"dist\Web.config" pw
Flag pw preserve whitespace, more options
ctt --help.