Support utils.FileExists/1

Support predicate for checking if a file exists on disk.

gopkgs/utils/utils.go

@@ -7,6 +7,7 @@ import (
 	"log"
 	"net/http"
 	"net/http/httputil"
+	"os"
 	"os/user"
 )
 
@@ -19,6 +20,15 @@ func HomeDir() string {
 	return user.HomeDir
 }
 
+// Return true if `path` exists and false otherwise.
+func FileExists(path string) bool {
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		return false
+	} else {
+		return true
+	}
+}
+
 // Call log.Fatal with `err` when it's not nil.
 func FailOn(err error) {
 	if err != nil {