From ba70bf7e3f8f83fea1f1b780525002dd7c735003 Mon Sep 17 00:00:00 2001
From: Jussi Pakkanen <jpakkane@gmail.com>
Date: Sun, 10 Mar 2013 01:53:24 +0200
Subject: [PATCH] Do not touch conf files if the new one would be identical to
 the old one.

---
 backends.py | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/backends.py b/backends.py
index 0aec6e2ea..9ac6fbfae 100755
--- a/backends.py
+++ b/backends.py
@@ -53,7 +53,16 @@ def do_conf_file(src, dst, variables):
             line = line.replace('@' + varname + '@', var)
             match = re.search(regex, line)
         result.append(line)
-    open(dst, 'w').writelines(result)
+    dst_tmp = dst + '~'
+    open(dst_tmp, 'w').writelines(result)
+    # If contents are identical, don't touch the file to prevent
+    # unnecessary rebuilds.
+    try:
+        if open(dst, 'r').read() == open(dst_tmp, 'r').read():
+            return
+    except FileNotFoundError:
+        pass
+    os.replace(dst_tmp, dst)
 
 
 class Backend():