contrib: Add script which helps bisecting avocado execution

This makes sure we setup and clean the environment before/after the
executed check. It comes from simple script I have been using for ages
and finally I took the time to add colors and some UI to allow running
on unstable environment.
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

contrib/scripts/avocado-bisect.sh

+#!/bin/sh
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; specifically version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See LICENSE for more details.
+#
+# Copyright: 2017 Red Hat, Inc.
+# Author: Lukas Doktor <ldoktor@redhat.com>
+
+#
+# This script helps with bisecting avocado sources by doing the prep
+# and cleanup work needed to successfully bisect avocado execution
+# Use it by running:
+#     $ git bisect start $BAD $GOOD
+#     $ git bisect run ./contrib/scripts/avocado-bisect.sh $YOUR_CMD
+#
+
+ERR=()
+INTERACTIVE=0
+
+case $1 in
+    "-h")
+    	echo "$0 [-h] [-i] [CHECK_CMD [...]]"
+    	echo "    -h         Show this help"
+        echo "    -i         On failure ask whether to ignore this failure"
+        echo "    CHECK_CMD  Check cmd(s), when not supplied 'make check' is used"
+        exit 1
+        ;;
+    "-i")
+        shift
+        INTERACTIVE=1
+        ;;
+esac
+
+
+run() {
+    echo -e "\n\e[32mRunning '$*'\e[0m"
+    eval $*
+    if [ $? != 0 ]; then
+        if [ $INTERACTIVE -eq 1 ]; then
+            echo -ne "\e[33mUse 'y' to ignore this failure: \e[0m"
+            read RES
+            [ "$RES" == "y" ] && echo -e "\e[33mStatus of $* overridden to PASS\[0m" && return 0
+        fi
+        echo -e "\e[31m$* FAILED\e[0m"
+        ERR+=("$1")
+    else
+        echo -e "\e[32m$* PASSED\e[0m\n"
+    fi
+}
+
+run "git log -1 --oneline"
+run "make develop"
+if [ "$*" ]; then
+    run $*
+else
+	run "make check"
+fi
+run "make clean"
+
+
+if [ "$ERR" ]; then
+    echo -e "\e[31m"
+    echo "Failed checks of commit $(git log -1 --oneline):"
+    for CMD in "${ERR[@]}"; do
+        echo -e " * $CMD FAILED"
+    done
+    echo -ne "\e[0m"
+else
+    echo -e "\e[32mAll checks PASSED\e[0m"
+fi
+if [ "$ERR" ]; then
+    exit 1
+fi
+exit 0