Systemd mount generator: Silence shellcheck warnings

Silences a warning about an intentionally unquoted variable.
Fixes a warning caused by strings split across lines by slightly
refactoring keyloadcmd.

Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Antonio Russo <antonio.e.russo@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: InsanePrawn <insane.prawny@gmail.com>
Closes #9649

etc/systemd/system-generators/zfs-mount-generator.in

@@ -60,6 +60,7 @@ process_line() {
   IFS="$(printf '\t')"
   # protect against special characters in, e.g., mountpoints
   set -f
+  # shellcheck disable=SC2086
   set -- $1
   dataset="${1}"
   p_mountpoint="${2}"
@@ -87,17 +88,19 @@ process_line() {
         pathdep="RequiresMountsFor='${p_keyloc#file://}'"
         keyloadcmd="@sbindir@/zfs load-key '${dataset}'"
       elif [ "${p_keyloc}" = "prompt" ] ; then
-        keyloadcmd="/bin/sh -c 'set -eu;"\
+        keyloadcmd="\
-"keystatus=\"\$\$(@sbindir@/zfs get -H -o value keystatus \"${dataset}\")\";"\
+/bin/sh -c '\
-"[ \"\$\$keystatus\" = \"unavailable\" ] || exit 0;"\
+set -eu;\
-"count=0;"\
+keystatus=\"\$\$(@sbindir@/zfs get -H -o value keystatus \"${dataset}\")\";\
-"while [ \$\$count -lt 3 ];do"\
+[ \"\$\$keystatus\" = \"unavailable\" ] || exit 0;\
-"  systemd-ask-password --id=\"zfs:${dataset}\""\
+count=0;\
-"    \"Enter passphrase for ${dataset}:\"|"\
+while [ \$\$count -lt 3 ];do\
-"    @sbindir@/zfs load-key \"${dataset}\" && exit 0;"\
+  systemd-ask-password --id=\"zfs:${dataset}\"\
-"  count=\$\$((count + 1));"\
+    \"Enter passphrase for ${dataset}:\"|\
-"done;"\
+    @sbindir@/zfs load-key \"${dataset}\" && exit 0;\
-"exit 1'"
+  count=\$\$((count + 1));\
+done;\
+exit 1'"
       else
         printf 'zfs-mount-generator: (%s) invalid keylocation\n' \
           "${dataset}" >/dev/kmsg