Add .shellcheckrc

Author: taiki-e

.shellcheckrc

@@ -0,0 +1,14 @@
+# ShellCheck configuration
+# https://github.com/koalaman/shellcheck/blob/HEAD/shellcheck.1.md#rc-files
+
+# See also:
+# https://www.shellcheck.net/wiki/Optional
+# https://google.github.io/styleguide/shellguide.html
+
+# https://www.shellcheck.net/wiki/SC2292
+# https://google.github.io/styleguide/shellguide.html#s6.3-tests
+enable=require-double-brackets
+
+# https://www.shellcheck.net/wiki/SC2250
+# https://google.github.io/styleguide/shellguide.html#s5.6-variable-expansion
+enable=require-variable-braces