feat: allow specifying a single process type to restart

This changes restarts to drop the 'release' part that currently gets triggered, which also helps reduce the possibility that a new image layer will be added due to predeploy deploy triggers.

Note that the old method essentially halfway-rebuilt the app (which was what added the extra layer). This refactor removes that, which is a bc-break.

Additionally, scaling processes will result in deploying _only_ restarting the processes being scaled.

Closes #2184

plugins/ps/subcommands.go

@@ -54,8 +54,11 @@ func CommandReport(appName string, format string, infoFlag string) error {
 }
 
 // CommandRestart restarts an app
-func CommandRestart(appName string, allApps bool, parallelCount int) error {
+func CommandRestart(appName string, processName string, allApps bool, parallelCount int) error {
 	if allApps {
+		if processName != "" {
+			return errors.New("Unable to restart all apps when specifying a process name")
+		}
 		return common.RunCommandAgainstAllApps(Restart, "restart", parallelCount)
 	}
 
@@ -63,6 +66,10 @@ func CommandRestart(appName string, allApps bool, parallelCount int) error {
 		return err
 	}
 
+	if processName != "" {
+		return RestartProcess(appName, processName)
+	}
+
 	return Restart(appName)
 }