From 148a356dde11df9e306e7e7e13204c59211a6074 Mon Sep 17 00:00:00 2001
From: Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>
Date: Tue, 22 Jan 2019 08:14:57 +0000
Subject: tcwg_kernel-bisect.sh: Better handle regressions in merges commits

At the moment we check only first parent of first_bad to confirm
that it is good.  This patch extends that to checking/finding
a good parent of merge commits.

Change-Id: I0cb38223e70b10531555615ca39f9d584948c751
---
 tcwg_kernel-bisect.sh | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/tcwg_kernel-bisect.sh b/tcwg_kernel-bisect.sh
index 61876313..24a0917b 100755
--- a/tcwg_kernel-bisect.sh
+++ b/tcwg_kernel-bisect.sh
@@ -198,8 +198,15 @@ if [ x"$res" = x"0" ]; then
     first_bad=$(cat .git/BISECT_RUN | head -n 1 | grep "is the first bad commit" | cut -d" " -f 1)
     assert [ x"$first_bad" != x"" ]
 
-    last_good=$(git rev-parse $first_bad^)
-    if ! grep -q $last_good "$artifacts/good_revs"; then
+    for last_good in $(git rev-parse $first_bad^@); do
+	if grep -q $last_good "$artifacts/good_revs"; then
+	    # One of immediate parrents of $first_bad tested good.
+	    break
+	fi
+	last_good=""
+    done
+    if [ x"$last_good" = x"" ]; then
+	# None of immediate parents of $first_bad tested as good.
 	# It seems that git-bisect assumes parent commit as "good" on
 	# the basis of one of its children being "good".  Therefore we
 	# can have a situation when we have parent P with children C1 and C2,
@@ -208,10 +215,26 @@ if [ x"$res" = x"0" ]; then
 	# and it knows CB is "bad", so git-bisect returns C1 as the first bad
 	# commit.
 	# To simplify investigations we explicitly test parent of $first_bad.
-	echo "Testing last_good $last_good (hoping for success)"
-	git checkout --detach "$last_good"
-	$artifacts/test.sh &
-	res=0 && wait $! || res=$?
+	res=0
+	for last_good in $(git rev-parse $first_bad^@); do
+	    if grep -q $last_good "$artifacts/bad_revs" "$artifacts/skipped_revs"; then
+		echo "First_bad's parent $last_good has tested bad or skipped"
+		last_good=""
+		continue
+	    fi
+	    if [ x"$(git merge-base $merge_base $last_good)" != x"$merge_base" ]; then
+		echo "First_bad's parent $last_good is outside of bisect scope"
+		last_good=""
+		continue
+	    fi
+	    echo "Testing first_bad's parent $last_good (hoping for success)"
+	    git checkout --detach "$last_good"
+	    $artifacts/test.sh &
+	    res=0 && wait $! || res=$?
+	    if [ x"$res" = x"0" ]; then
+		break
+	    fi
+	done
 	if [ x"$res" != x"0" ]; then
 	    # It seems $last_good was on a path that tested good, even though
 	    # it itself is bad.  We re-trigger the bisection job with updated
-- 
cgit v1.2.3