Move git and url checks into pkg

This moves the IsGIT and IsURL functions out of the generic `utils`
package and into their own `urlutil` pkg.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

urlutil/git.go

@@ -0,0 +1,30 @@
+package urlutil
+
+import "strings"
+
+var (
+	validPrefixes = []string{
+		"git://",
+		"github.com/",
+		"git@",
+	}
+)
+
+// IsGitURL returns true if the provided str is a git repository URL.
+func IsGitURL(str string) bool {
+	if IsURL(str) && strings.HasSuffix(str, ".git") {
+		return true
+	}
+	for _, prefix := range validPrefixes {
+		if strings.HasPrefix(str, prefix) {
+			return true
+		}
+	}
+	return false
+}
+
+// IsGitTransport returns true if the provided str is a git transport by inspecting
+// the prefix of the string for known protocols used in git.
+func IsGitTransport(str string) bool {
+	return IsURL(str) || strings.HasPrefix(str, "git://") || strings.HasPrefix(str, "git@")
+}