Check shell scripts for POSIX sh compliance

The hook functions and script might be executeted by busybox. Mark those
files as POSIX sh for shellcheck.

Signed-off-by: Benjamin Drung <benjamin.drung@canonical.com>

.shellcheckrc

@@ -5,3 +5,8 @@ disable=SC1090
 # SC1091: Not following <file>
 # https://www.shellcheck.net/wiki/SC1091
 disable=SC1091
+
+# SC3043: In POSIX sh, local is undefined
+# https://www.shellcheck.net/wiki/SC3043
+# ...but dash and BusyBox ash support it.
+disable=SC3043

debian/salsa-ci.yml

@@ -20,5 +20,5 @@ shellcheck:
     - apt-get update
     - apt-get install -y shellcheck
     - |
-        shellcheck -s dash hook-functions $(find hooks scripts -type f) $({ find . -maxdepth 1 -type f -executable; find debian -maxdepth 1 -type f; find docs kernel -type f; } | xargs grep -l '^#!/bin/sh')
+        shellcheck hook-functions $(find hooks scripts -type f) $({ find . -maxdepth 1 -type f -executable; find debian -maxdepth 1 -type f; find docs kernel -type f; } | xargs grep -l '^#!/bin/sh')
   needs: []

hook-functions

@@ -1,4 +1,5 @@
 # -*- shell-script -*-
+# shellcheck shell=sh
 
 catenate_cpiogz() {
 	# Sanity check

scripts/functions

@@ -1,4 +1,5 @@
 # -*- shell-script -*-
+# shellcheck shell=sh
 
 _log_msg()
 {

scripts/local

@@ -1,4 +1,5 @@
 # Local filesystem mounting			-*- shell-script -*-
+# shellcheck shell=sh
 
 local_top()
 {

scripts/nfs

@@ -1,4 +1,5 @@
 # NFS filesystem mounting			-*- shell-script -*-
+# shellcheck shell=sh
 
 # FIXME This needs error checking