Fix shellcheck complaints

Author: dsessler7

internal/pgbackrest/config.go

@@ -287,9 +287,14 @@ func DedicatedSnapshotVolumeRestoreCommand(pgdata string, tablespaceVolumes []*c
 	// Otherwise return 1, Job will fail, and we will not proceed with snapshot.
 	restoreScript := `declare -r pgdata="$1" opts="$2"
 BACKUP_LABEL="xxx"
-if [ -e "` + pgdata + `/backup_label" ]
+if [[ -e "` + pgdata + `/backup_label" ]]
 then
-  BACKUP_LABEL=$(md5sum ` + pgdata + `/backup_label | awk '{print $1}')
+  if BACKUP_LABEL=$(md5sum ` + pgdata + `/backup_label); then
+    BACKUP_LABEL=$(echo "${BACKUP_LABEL}" | awk '{print $1}')
+  else
+    echo "Error getting checksum of backup_label."
+    exit 1
+  fi
 fi
 echo "Starting pgBackRest delta restore"
 
@@ -299,11 +304,16 @@ bash -xc "pgbackrest restore ${opts}"
 rm -f "${pgdata}/patroni.dynamic.json"
 
 BACKUP_LABEL_POST="xxx"
-if [ -e "` + pgdata + `/backup_label" ]
+if [[ -e "` + pgdata + `/backup_label" ]]
 then
-  BACKUP_LABEL_POST=$(md5sum ` + pgdata + `/backup_label | awk '{print $1}')
+  if BACKUP_LABEL_POST=$(md5sum ` + pgdata + `/backup_label); then
+    BACKUP_LABEL_POST=$(echo "${BACKUP_LABEL_POST}" | awk '{print $1}')
+  else
+    echo "Error getting checksum of backup_label."
+    exit 1
+  fi
 fi
-if [ "$BACKUP_LABEL" != "$BACKUP_LABEL_POST" ]
+if [[ "${BACKUP_LABEL}" != "${BACKUP_LABEL_POST}" ]]
 then
   exit 0
 fi