Prow: Add shellcheck to openshift/installer

.travis.yml

@@ -20,12 +20,7 @@ jobs:
         '{extends: default, rules: {line-length: {level: warning, max: 120}}}' 
         ./examples/ ./installer/
       name: YAML lint
-    - script: >
-        docker run -v $(pwd):/workdir:ro
-        --entrypoint sh quay.io/coreos/shellcheck-alpine:v0.5.0
-        -c 'for file in $(find /workdir/ -type f -name "*.sh"); do
-        if ! shellcheck --format=gcc $file; then export FAILED=true; fi; done;
-        if [ "$FAILED" != "" ]; then exit 1; fi'
+    - script: ./hack/shellcheck.sh
       name: shellcheck
     - script: "docker run -v $PWD:/go/src/github.com/openshift/installer -w /go/src/github.com/openshift/installer quay.io/coreos/golang-testing go vet ./installer/..."
       name: Go vet

hack/shellcheck.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+DIR="${1:-.}"
+if [ "$IS_CONTAINER" != "" ]; then
+  find "${DIR}" -type f -name '*.sh' -exec shellcheck --format=gcc {} \+
+else
+  docker run -e IS_CONTAINER='TRUE' --rm -v "$(realpath "${DIR}")":/workdir:ro --entrypoint sh quay.io/coreos/shellcheck-alpine:v0.5.0 /workdir/hack/shellcheck.sh /workdir;
+fi;