Add gocyclo

The `gocyclo` tool call can be used via a make target to test function
complexity.

Makefile

@@ -25,7 +25,7 @@ all: test
 clean:
 	@rm -rf $(dir $(realpath $(firstword $(MAKEFILE_LIST))))/binaries
 
-sanity-check: unused misspell lint fmt vet
+sanity-check: unused misspell lint fmt vet gocyclo
 
 vet:
 	@$(dir $(realpath $(firstword $(MAKEFILE_LIST))))/scripts/go-vet.sh
@@ -36,6 +36,9 @@ fmt:
 lint:
 	@$(dir $(realpath $(firstword $(MAKEFILE_LIST))))/scripts/go-lint.sh
 
+gocyclo:
+	@$(dir $(realpath $(firstword $(MAKEFILE_LIST))))/scripts/go-cyclo.sh
+
 unused:
 	@$(dir $(realpath $(firstword $(MAKEFILE_LIST))))/scripts/unused.sh
 

scripts/go-cyclo.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+
+# Copyright © 2018 Matthias Diester
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+set -euo pipefail
+
+if ! hash gocyclo > /dev/null 2>&1; then
+  echo 'Unable to find tool `gocyclo` in the path. Run `go get github.com/fzipp/gocyclo` to install it.'
+  exit 1
+fi
+
+BASEDIR="$(cd "$(dirname "$0")/.." && pwd)"
+
+( cd $BASEDIR && find . -path ./vendor -prune -o -type f -name "*.go" -exec dirname {} \; | sort -u | xargs gocyclo -over 25 )