What it does
The watch goal runs the CDS build and starts the application, and with Devtools on the project it takes advantage of their reload mechanism, where any change reloads the application context instead of restarting the whole application.
Conditions
Spring Boot Devtools are on the project, without which the goal performs a complete restart of the application after a CDS model change, which capire calls slower; on Windows the watch goal only works if the Spring Boot Devtools are enabled
Remaining work
Add the Devtools dependency, and the plugin group com.sap.cds to ~/.m2/settings.xml for the short mvn cds:watch form. Devtools detects changes to .class files only, so a change to Java code is picked up once the build has produced them.