DCli warmup essentially does the same as a pub get. It is provided as a convenience function and you can use a dart pub get interchangeably with DCli warmup.
DCli warmup prepares your project so that you can run any of the project scripts.
When a script is run that has been 'warmed' up, it runs in JIT mode and as such has a slower start time when compared to a compiled script.
The advantage of JIT mode is that it makes it easy to iterate over code changes. You can simply edit your script and immediately run the script.
You only need to run warmup again if you make a change to your dependencies.
If you edit pubspec.yaml in your project then you need to run
dcli warmupso that DCli sees the changes you have made.
If you change your pubspec.yaml you can call `dcli warmup` from anywhere in your project's directory structure.