tcwg_kernel-bisect.sh: Handle git-bisect's smartness.

Handle transitive assumptions of git-bisect about parent commits.
See inline comment for details.

Change-Id: I28e35b249e43325f37155059de4ec356cf140de4

1 files changed, 25 insertions, 1 deletions

diff --git a/tcwg_kernel-bisect.sh b/tcwg_kernel-bisect.sh
index dada7b39..ec54d1f7 100755
--- a/tcwg_kernel-bisect.sh
+++ b/tcwg_kernel-bisect.sh
@@ -55,6 +55,7 @@ EOF
 	exit 0
     fi
     mv "$artifacts/build-bad" "$artifacts/build-$bad_rev-bad"
+    echo "$bad_rev" >> $artifacts/bad_revs
 elif [ x"$bad_rev" = x"default" ]; then
     echo "ERROR: Need explicit --bad_rev"
     exit 1
@@ -80,7 +81,8 @@ cd $current_project
 # Remember $good_rev from the baseline build above.
 good_rev=$(git rev-parse HEAD)
 baseline_rev="$good_rev"
-mv "$artifacts/build-baseline" "$artifacts/build-$good_rev-baseline"
+mv "$artifacts/build-baseline" "$artifacts/build-$baseline_rev-baseline"
+echo "$baseline_rev" >> $artifacts/good_revs
 
 # Bisect script.
 #
@@ -116,10 +118,13 @@ $scripts/tcwg_kernel-build.sh \
   --verbose "$verbose" &
 res=0 && wait \$! || res=\$?
 if [ -f $artifacts/build-\$rev/failures ]; then
+  echo "\$rev" >> $artifacts/bad_revs
   exit 1
 elif [ x"\$res" != x"0" ]; then
+  echo "\$rev" >> $artifacts/skipped_revs
   exit 125
 else
+  echo "\$rev" >> $artifacts/good_revs
   exit 0
 fi
 EOF
@@ -244,6 +249,25 @@ if [ -f $artifacts/first-bad ]; then
     fi
 
     last_good=$(git -C $current_project rev-parse $first_bad^)
+    if ! grep -q $last_good "$artifacts/good_revs"; then
+	# 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,
+	# and child C1 has a child of its own CB.  Git-bisect tests C2 as
+	# "good", and CB as "bad".  From C2 being good it assumes P as "good",
+	# 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"
+	../bisect-run.sh &
+	res=0 && wait $! || res=$?
+	if [ x"$res" != x"0" ]; then
+	    echo "ERROR: build for last_good $last_good failed"
+	    exit 1
+	fi
+    fi
+
     if [ x"$last_good" != x"$baseline_rev" ]; then
 	mv "$artifacts/build-$last_good" "$artifacts/build-$last_good-last_good"
     else