Add shfmt to the validate make target

We need to run on a directory since shell files might have no extension.
There are few shell files, so speed should not be an issue.

Fixes #1166.

Dockerfile

@@ -36,6 +36,15 @@ RUN mkdir -p /usr/src/criu \
     && cd /usr/src/criu \
     && make install-criu
 
+# install shfmt
+RUN mkdir -p /go/src/github.com/mvdan \
+    && cd /go/src/github.com/mvdan \
+    && git clone https://github.com/mvdan/sh \
+    && cd sh \
+    && git checkout -f v0.4.0 \
+    && go install ./cmd/shfmt \
+    && rm -rf /go/src/github.com/mvdan
+
 # setup a playground for us to spawn containers in
 ENV ROOTFS /busybox
 RUN mkdir -p ${ROOTFS} \

Makefile

@@ -119,6 +119,7 @@ clean:
 
 validate:
 	script/validate-gofmt
+	script/validate-shfmt
 	go vet ./...
 
 ci: validate localtest

script/validate-shfmt

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+badFiles=()
+while read f; do
+	badFiles+=("$f")
+done < <(shfmt -l . | grep -v Godeps/)
+
+if [ ${#badFiles[@]} -eq 0 ]; then
+	echo 'Congratulations!  All shell source files are properly formatted.'
+else
+	{
+		echo "These files are not properly shfmt'd:"
+		for f in "${badFiles[@]}"; do
+			echo " - $f"
+		done
+		echo
+		echo 'Please reformat the above files using "shfmt -w" and commit the result.'
+		echo
+	} >&2
+	false
+fi