add verify git read func

vendor/gopkg.in/src-d/go-git.v4/common.go

@@ -0,0 +1,22 @@
+package git
+
+import "strings"
+
+const defaultDotGitPath = ".git"
+
+// countLines returns the number of lines in a string à la git, this is
+// The newline character is assumed to be '\n'.  The empty string
+// contains 0 lines.  If the last line of the string doesn't end with a
+// newline, it will still be considered a line.
+func countLines(s string) int {
+	if s == "" {
+		return 0
+	}
+
+	nEOL := strings.Count(s, "\n")
+	if strings.HasSuffix(s, "\n") {
+		return nEOL
+	}
+
+	return nEOL + 1
+}