From d964add08d8d8c114a31c0957cb89f130508d933 Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter@pcc.me.uk>
Date: Thu, 27 Apr 2017 17:04:05 +0000
Subject: [PATCH] cmake: Touch $GIT_DIR/logs/HEAD if it does not already exist.

Apparently some git tools (such as "repo") may not create this file.
Patch by Quentin Neill.

llvm-svn: 301565
---
 include/llvm/Support/CMakeLists.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/llvm/Support/CMakeLists.txt b/include/llvm/Support/CMakeLists.txt
index b4b99370574..825052171cd 100644
--- a/include/llvm/Support/CMakeLists.txt
+++ b/include/llvm/Support/CMakeLists.txt
@@ -18,6 +18,10 @@ macro(find_first_existing_vc_file out_var path)
   if(git_result EQUAL 0)
     string(STRIP "${git_dir}" git_dir)
     set(${out_var} "${git_dir}/logs/HEAD")
+    # some branchless cases (e.g. 'repo') may not yet have .git/logs/HEAD
+    if (NOT EXISTS "${git_dir}/logs/HEAD")
+      file(WRITE "${git_dir}/logs/HEAD" "")
+    endif()
   else()
     find_first_existing_file(${out_var}
       "${path}/.svn/wc.db"   # SVN 1.7