Add lint script; run it on circle. Intentionally don't lint static.go.

bin/lint

@@ -0,0 +1,87 @@
+#!/bin/bash
+# This scipt lints go files for common errors.
+#
+# Its runs gofmt and go vet, and optionally golint and
+# gocyclo, if they are installed.
+#
+# With no arguments, it lints the current files staged
+# for git commit.  Or you can pass it explicit filenames
+# (or directories) and it will lint them.
+#
+# To use this script automatically, run:
+#   ln -s ../../bin/lint .git/hooks/pre-commit
+
+set -eu
+
+function lint_go {
+	filename="$1"
+	result=0
+
+	if [ -n "$(gofmt -s -l "${filename}")" ]; then
+		result=1
+		echo "${filename}: run gofmt -s -w ${filename}!"
+	fi
+
+	go tool vet "${filename}" || result=$?
+
+	# golint is completely optional.  If you don't like it
+	# don't have it installed.
+	if type golint >/dev/null 2>&1; then
+		# golint doesn't set an exit code it seems
+		lintoutput=$(golint "${filename}")
+		if [ "$lintoutput" != "" ]; then
+			result=1
+			echo "$lintoutput"
+		fi
+	fi
+
+	# gocyclo is completely optional.  If you don't like it
+	# don't have it installed.  Also never blocks a commit,
+	# it just warns.
+	if type gocyclo >/dev/null 2>&1; then
+		gocyclo -over 25 "${filename}" | while read line; do
+			echo "${filename}": higher than 25 cyclomatic complexity - "${line}"
+		done
+	fi
+
+	return $result
+}
+
+function lint {
+	filename="$1"
+	ext="${filename##*\.}"
+
+	# Don't lint deleted files
+	if [ ! -f "$filename" ]; then
+		return
+	fi
+
+	# Don't lint this script or static.go
+	case "${filename}" in
+	bin/lint) return;;
+	./app/static.go) return;;
+	esac
+
+	case "$ext" in
+		go) lint_go "${filename}"
+		;;
+	esac
+}
+
+function lint_files {
+	lint_result=0
+	while read filename; do
+		lint "${filename}" || lint_result=1
+	done
+	exit $lint_result
+}
+
+function list_files {
+	if [ $# -gt 0 ]; then
+		find "$@" -type f
+	else
+		git diff --cached --name-only
+	fi
+}
+
+list_files "$@" | lint_files