Add setup/enmod.sh to enable setup mods

setup/enmod.sh

@@ -0,0 +1,51 @@
+#!/bin/bash
+
+. /etc/mailinabox.conf || exit 1
+. setup/functions.sh
+
+if [ -z "${1:-}" ]; then
+    echo "usage: $0 <name-of-setup-mod>"
+    echo "   eg: $0 remote-nextcloud"
+    echo "For a list of available setup mods, see directory setup/mods.available"
+    exit 1
+fi
+
+# determine the path to the mod specified and validate it
+case "$1" in
+    */* )
+        mod_fn="$1"
+        ;;
+    *.sh )
+        mod_fn="setup/mods.available/$1"
+        ;;
+    * )
+        mod_fn="setup/mods.available/$1.sh"
+        ;;
+esac
+
+if [ ! -e "$mod_fn" ]; then
+    echo "DOES NOT EXIST: $mod_fn" 1>&2
+    exit 1
+elif [ ! -f "$mod_fn" ]; then
+    echo "NOT A FILE: $mod_fn" 1>&2
+    exit 1
+elif [ ! -x "$mod_fn" ]; then
+    echo "NOT EXECUTABLE: $mod_fn" 1>&2
+    exit 1
+fi
+
+# create the enabled mods directory if it doesn't exist
+mkdir -p "${LOCAL_MODS_DIR:-local}"
+
+# if the mod is already enabled, we can exit now
+link_fn="${LOCAL_MODS_DIR:-local}/$(basename "$mod_fn")"
+if [ -s "$link_fn" -a -f "$link_fn" -a -x "$link_fn" ]; then
+    echo "Setup mod '$1' already enabled ($link_fn)"
+    exit 0
+fi
+
+# create the symlink
+ln -sf \
+    "$(realpath --relative-to="${LOCAL_MODS_DIR:-local}" "$mod_fn")" \
+    "$link_fn"
+echo "Setup mod '$1' enabled (created symlink: $link_fn)"