feat(travis): run shellcheck during lint job

* saltstack-formulas/template-formula#180 (comment)

.travis.yml

@@ -27,6 +27,9 @@ jobs:
       name: 'Lint: salt-lint, yamllint, rubocop & commitlint'
       before_install: 'skip'
       script:
+        # Run `shellcheck`
+        - git ls-files | grep '\.sh$\|\.bash$\|\.ksh$'
+                       | xargs shellcheck
         # Install and run `salt-lint`
         - pip install --user salt-lint
         - git ls-files | grep '\.sls$\|\.jinja$\|\.j2$\|\.tmpl$\|\.tst$'

ssf/defaults.yaml

@@ -22,8 +22,8 @@ ssf_node_anchors:
             #       An alternative method could be to use:
             #       `git describe --abbrev=0 --tags`
             # yamllint disable rule:line-length
-            title: 'ci(travis): use default matrix after `centos-6` image fix'
-            body: '* Automated using https://github.com/myii/ssf-formula/pull/105'
+            title: 'ci(travis): run `shellcheck` during lint job [skip ci]'
+            body: '* Automated using https://github.com/myii/ssf-formula/pull/106'
             # yamllint enable rule:line-length
           github:
             owner: 'saltstack-formulas'

ssf/files/default/.travis.yml

@@ -118,6 +118,9 @@ jobs:
       name: '{{ name_linters }}'
       before_install: 'skip'
       script:
+        # Run `shellcheck`
+        - git ls-files | grep '\.sh$\|\.bash$\|\.ksh$'
+                       | xargs shellcheck
         {#- Prepare variable used for `pip` #}
         {%- set pip_cmd = 'pip' %}
         {%- if semrel_formula == 'ufw' %}