refactor shouldRun to be easier to read

README.md

@@ -315,7 +315,7 @@ Each command type supports the following options:
 - `no_auto`: if set to `true` the command will not be executed automatically, but can be executed manually using the `--only` flag.
 - `local`: if set to `true` the command will be executed on the local host (the one running the `spot` command) instead of the remote host(s).
 - `sudo`: if set to `true` the command will be executed with `sudo` privileges.
-- `only_on`: optional, allows to set a list of host names or addresses where the command will be executed. If not set, the command will be executed on all hosts.
+- `only_on`: optional, allows to set a list of host names or addresses where the command will be executed. If not set, the command will be executed on all hosts. For example, `only_on: [host1, host2]` will execute command on `host1` and `host2` only. This option also supports reversed condition, so if user wants to execute command on all hosts except some, `!` prefix can be used. For example, `only_on: [!host1, !host2]` will execute command on all hosts except `host1` and `host2`. 
 
 example setting `ignore_errors`, `no_auto` and `only_on` options:
 

pkg/runner/runner.go

@@ -252,30 +252,17 @@ func (p *Process) shouldRunCmd(onlyOn []string, hostName, hostAddr string) bool
 		return true
 	}
 
-	isExcluded := func(host string) bool {
-		return strings.HasPrefix(host, "!") &&
-			(hostName == strings.TrimPrefix(host, "!") || hostAddr == strings.TrimPrefix(host, "!"))
-	}
-
-	isIncluded := func(host string) bool {
-		return !strings.HasPrefix(host, "!") && (hostName == host || hostAddr == host)
-	}
-
 	for _, host := range onlyOn {
-		if isExcluded(host) {
-			return false
+		if strings.HasPrefix(host, "!") { // exclude host
+			if hostName == host[1:] || hostAddr == host[1:] {
+				return false
+			}
+			continue
 		}
-		if isIncluded(host) {
+		if hostName == host || hostAddr == host { // include host
 			return true
 		}
 	}
 
-	// Default to running if there were no inclusions.
-	for _, host := range onlyOn {
-		if !strings.HasPrefix(host, "!") {
-			return false
-		}
-	}
-
-	return true
+	return false
 }