export unprefix in utils and fix error msg

1 files changed, 14 insertions, 0 deletions

diff --git a/utils/string.go b/utils/string.go
new file mode 100644
index 0000000..b3cbb17
--- /dev/null
+++ b/utils/string.go
@@ -0,0 +1,14 @@
+package utils
+
+import (
+	"fmt"
+	"strings"
+)
+
+func Unprefix(path string, prefix string) (string, error) {
+	if !strings.HasPrefix(path, prefix) {
+		return path, fmt.Errorf("%q is not prefixed by %q", path, prefix)
+	} else {
+		return path[len(prefix):], nil
+	}
+}