Show a warning when using wrong executable

This commit updates the 'wdcli' command to show a warning when using the
wrong executable.

env/constants.go

@@ -0,0 +1,36 @@
+package env
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/FAU-CDI/wisski-distillery/internal/fsx"
+)
+
+// Executable is the name of the 'wdcli' executable.
+// It should be located inside the deployment directory.
+const Executable = "wdcli"
+
+// ExecutablePath returns the path to the executable of this distillery.
+func (dis *Distillery) ExecutablePath() string {
+	return filepath.Join(dis.Config.DeployRoot, Executable)
+}
+
+// UsingDistilleryExecutable checks if the current process
+func (dis *Distillery) UsingDistilleryExecutable() bool {
+	exe, err := os.Executable()
+	if err != nil {
+		return false
+	}
+	return fsx.SameFile(exe, dis.ExecutablePath())
+}
+
+// Config file is the name of the config file.
+// It should be located inside the deployment directory.
+const ConfigFile = ".env"
+
+// ConfigFilePath returns the path to the configuration file of this distillery.
+// TODO: This should be moved to the Config struct.
+func (dis *Distillery) ConfigFilePath() string {
+	return filepath.Join(dis.Config.DeployRoot, ConfigFile)
+}