Add a threshold based golint test case

This lets some golint errors in, but fails if you're over a certain
threshold. The current threshold of 15% (of LOC) is arbitrary and
subject to change. The algorithm should be extended to check a range of
commits, although it's unclear how to detect what range of commits make
up a patch set.

test/test-golint.sh

@@ -0,0 +1,52 @@
+#!/bin/bash
+# check that go lint passes or doesn't get worse by some threshold
+echo running test-golint.sh
+# FIXME: test a range of commits, since only the last patch is checked here
+PREVIOUS='HEAD^'
+CURRENT='HEAD'
+THRESHOLD=15	# percent problems per new LOC
+XPWD=`pwd`
+ROOT="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && cd .. && pwd )"	# dir!
+cd "${ROOT}" >/dev/null
+
+LINT=`golint`	# current golint output
+COUNT=`echo -e "$LINT" | wc -l`	# number of golint problems in current branch
+
+T=`mktemp --tmpdir -d tmp.XXX`
+[ "$T" = "" ] && exit 1
+cd $T || exit 1
+git clone --recursive "${ROOT}" 2>/dev/null	# make a copy
+cd "`basename ${ROOT}`" >/dev/null || exit 1
+
+DIFF1=0
+NUMSTAT1=`git diff "$PREVIOUS" "$CURRENT" --numstat`	# numstat diff since previous commit
+while read -r line; do
+	add=`echo "$line" | cut -f1`
+	# TODO: should we only count added lines, or count the difference?
+	sum="$add"
+	#del=`echo "$line" | cut -f2`
+	#sum=`expr $add - $del`
+	DIFF1=`expr $DIFF1 + $sum`
+done <<< "$NUMSTAT1"	# three < is the secret to putting a variable into read
+
+git checkout "$PREVIOUS" 2>/dev/null	# previous commit
+LINT1=`golint`
+COUNT1=`echo -e "$LINT1" | wc -l`	# number of golint problems in older branch
+
+# clean up
+cd "$XPWD" >/dev/null
+rm -rf "$T"
+
+[ "$LINT1" = "" ] && echo PASS && exit	# everything is "perfect"
+DELTA=$(printf "%.0f\n" `echo "(($COUNT1 - $COUNT) / $DIFF1) * 100" | bc -l`)
+
+echo "Lines of code: $DIFF1"
+echo "Prev. # of issues: $COUNT"
+echo "Curr. # of issues: $COUNT1"
+echo "Issue count delta is: $DELTA %"
+if [ "$DELTA" -gt "$THRESHOLD" ]; then
+	echo "Maximum threshold is: $THRESHOLD %"
+	echo '`golint` FAIL'
+	exit 1
+fi
+echo PASS