From 3ddb6d1833a94e3d141116f3e579e66ebef04111 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Tue, 16 Apr 2019 16:24:51 +0200
Subject: [PATCH] Allow refs to start with a digit

E.g. we want to accept "19.03" as a ref.
---
 src/libexpr/primops/flakeref.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libexpr/primops/flakeref.cc b/src/libexpr/primops/flakeref.cc
index 4127e63cc..973987469 100644
--- a/src/libexpr/primops/flakeref.cc
+++ b/src/libexpr/primops/flakeref.cc
@@ -5,7 +5,7 @@
 namespace nix {
 
 // A Git ref (i.e. branch or tag name).
-const static std::string refRegex = "[a-zA-Z][a-zA-Z0-9_.-]*"; // FIXME: check
+const static std::string refRegex = "[a-zA-Z0-9][a-zA-Z0-9_.-]*"; // FIXME: check
 
 // A Git revision (a SHA-1 commit hash).
 const static std::string revRegexS = "[0-9a-fA-F]{40}";