How can I deploy with conditional build commands?

You may find you need to use different build commands for different environments, in this case, you can usually use something similar to the following:

gulp build --%environment%

Which would result in gulp build --production or gulp build --staging etc. as necessary. You can set your environment on a per server basis.

However, if you need to be a bit more specific, or maybe have a more complex set of build commands per server, you could use a conditional build command as follows:

if [ "%environment%" == "production" ]; then
  // Production commands
else
  // Other commands
fi