From 24b5db53672843647da29073060bff3f81b05b90 Mon Sep 17 00:00:00 2001
From: Mike McQuaid <mike@mikemcquaid.com>
Date: Thu, 11 Aug 2016 13:47:13 +0100
Subject: [PATCH] update.sh: further tweak update fix.

---
 Library/Homebrew/cmd/update.sh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Library/Homebrew/cmd/update.sh b/Library/Homebrew/cmd/update.sh
index b32302cc0d..8078578a37 100644
--- a/Library/Homebrew/cmd/update.sh
+++ b/Library/Homebrew/cmd/update.sh
@@ -479,11 +479,13 @@ EOS
 
     PREFETCH_REVISION_VAR="PREFETCH_REVISION$TAP_VAR"
     PREFETCH_REVISION="${!PREFETCH_REVISION_VAR}"
+    POSTFETCH_REVISION="$(git rev-parse -q --verify refs/remotes/origin/"$UPSTREAM_BRANCH")"
 
     if [[ -n "$HOMEBREW_SIMULATE_FROM_CURRENT_BRANCH" ]]
     then
       simulate_from_current_branch "$DIR" "$TAP_VAR" "$UPSTREAM_BRANCH" "$CURRENT_REVISION"
-    elif [[ "$PREFETCH_REVISION" = "$CURRENT_REVISION" ]]
+    elif [[ "$PREFETCH_REVISION" = "$POSTFETCH_REVISION" ]] &&
+         [[ "$CURRENT_REVISION" = "$POSTFETCH_REVISION" ]]
     then
       export HOMEBREW_UPDATE_BEFORE"$TAP_VAR"="$CURRENT_REVISION"
       export HOMEBREW_UPDATE_AFTER"$TAP_VAR"="$CURRENT_REVISION"