cmd: provide feedback if OLLAMA_MODELS is set on non-serve command (#3470)

This also moves the checkServerHeartbeat call out of the "RunE" Cobra
stuff (that's the only word I have for that) to on-site where it's after
the check for OLLAMA_MODELS, which allows the helpful error message to
be printed before the server heartbeat check. This also arguably makes
the code more readable without the magic/superfluous "pre" function
caller.

cmd/cmd.go

@@ -226,6 +226,14 @@ func createBlob(cmd *cobra.Command, client *api.Client, path string) (string, er
 }
 
 func RunHandler(cmd *cobra.Command, args []string) error {
+	if os.Getenv("OLLAMA_MODELS") != "" {
+		return errors.New("OLLAMA_MODELS must only be set for 'ollama serve'")
+	}
+
+	if err := checkServerHeartbeat(cmd, args); err != nil {
+		return err
+	}
+
 	client, err := api.ClientFromEnvironment()
 	if err != nil {
 		return err
@@ -951,11 +959,10 @@ func NewCLI() *cobra.Command {
 	showCmd.Flags().Bool("system", false, "Show system message of a model")
 
 	runCmd := &cobra.Command{
-		Use:     "run MODEL [PROMPT]",
-		Short:   "Run a model",
-		Args:    cobra.MinimumNArgs(1),
-		PreRunE: checkServerHeartbeat,
-		RunE:    RunHandler,
+		Use:   "run MODEL [PROMPT]",
+		Short: "Run a model",
+		Args:  cobra.MinimumNArgs(1),
+		RunE:  RunHandler,
 	}
 
 	runCmd.Flags().Bool("verbose", false, "Show timings for response")