Add test.sh which uses shellcheck linter

README.md

@@ -109,6 +109,8 @@ If you have java installed, you can automatically get the build script to sign a
 
 To build your own custom pack, refer to custom-pack.md in the conf directory.
 
+Any changes made to the code should ideally be tested with test.sh, which runs the shellcheck linter program on every script.
+
 ### Credits
  - Thanks to @osm0sis for the base magisk/recovery code and inspiration and guidance on the majority of the stuff in here.
  - Thanks to @Setialpha, the creator of NanoDroid, and ale5000 for the lib installation code, permissions code, and patched play.

test.sh

@@ -0,0 +1,42 @@
+#!/bin/sh
+
+# Test the code with shellcheck
+#
+# Copyright 2018-2020 FriendlyNeighborhoodShane
+# Distributed under the terms of the GNU GPL v3
+
+abort() {
+  echo " " >&2;
+  echo "!!! FATAL ERROR: $1" >&2;
+  echo " " >&2;
+  [ -d "$tmpdir" ] && rm -rf "$tmpdir";
+  exit 1;
+}
+
+workdir="$(pwd)";
+cd "$workdir" || abort "Can't cd to $workdir";
+
+echo " ";
+echo "--        Minimal MicroG Test Script        --";
+echo "--     The Essentials only MicroG pack      --";
+echo "--      From the MicroG Telegram group      --";
+echo "--         No, not the Official one         --";
+
+for bin in shellcheck; do
+  [ "$(which $bin)" ] || abort "No $bin found";
+done;
+
+# These tests are only excluded in the command because they're pointless
+# We don't need to do them and they only cloud the output
+
+# SC1087: braces for array expansion
+  # False positive from extended regex
+  # Arrays aren't in sh anyway
+# SC1090: non-constant source
+# SC2034: assigned but not used
+# SC2154: used but not assigned
+  # All three happen all the time due to sourcing
+  # Can't add directives because it's all dynamic
+
+echo " ";
+shellcheck -s sh -e 1087,1090,2034,2154 -- "$workdir/src/META-INF/com/google/android/update-binary" "$workdir/build.sh" "$workdir/test.sh" "$workdir/update.sh" "$workdir"/conf/*.txt;