Provide informative exit codes

Blubee continues to backup the items in the 'backup.json' even if there
is an error with some item. This is useful as a partial backup is often
better than no backup. However, when there are alot of items to backup
the error might be hidden in the output and the user may not be aware
that something went wrong. Especially if one is using blubee in a
script, as the final exit code of blubee will be 0. To avoid this we
make sure to detect when ever an item fails to backup and exit with an
approperiate exit code, to notify the caller that something went wrong.

To make it easier to find the error we also provide some logs that may
help the user identify the issue.

backup.sh

@@ -10,27 +10,37 @@ backup_version="$(date '+%Y%m%d_%H%M%S')"
 
 while getopts ":s:d:r:xh:u:v:p:" option; do
     case "${option}" in
-        d)
-            destination_root=${OPTARG};;
-        s)
-            source_paths=${OPTARG};;
-        r)
-            source_root=${OPTARG};;
-        x)
-            dry_run="--dry-run";;
-        u)
-            user=${OPTARG};;
-        h)
-            host=${OPTARG};;
-        p)
-            port=${OPTARG};;
-        v)
-            backup_version=${OPTARG};;
-        :)
-            echo "Missing argument for option $OPTARG"
-            exit 1;;
-        ?)
-            echo "Unrecognized option '$OPTARG'";;
+    d)
+        destination_root=${OPTARG}
+        ;;
+    s)
+        source_paths=${OPTARG}
+        ;;
+    r)
+        source_root=${OPTARG}
+        ;;
+    x)
+        dry_run="--dry-run"
+        ;;
+    u)
+        user=${OPTARG}
+        ;;
+    h)
+        host=${OPTARG}
+        ;;
+    p)
+        port=${OPTARG}
+        ;;
+    v)
+        backup_version=${OPTARG}
+        ;;
+    :)
+        echo "Missing argument for option $OPTARG"
+        exit 1
+        ;;
+    ?)
+        echo "Unrecognized option '$OPTARG'"
+        ;;
     esac
 done
 
@@ -68,31 +78,69 @@ test_nonexistent_link "$latest_link" "$message" "$host" "$user" "$port"
 
 index=0
 source_path="$(dequote_string "$(get_list_item "$source_paths" "$index")")"
+if [ "$?" -ne "0" ]; then
+    echo "Could not get source paths from ${source_paths}, json may be malformed"
+    exit 4
+fi
+
+exit_code=0
 while [ "$source_path" != "null" ]; do
     source_suffix=$(trim_right_slash "$(trim_left_slash "$source_path")")
     backup_path_suffix=$(trim_right_slash "$(trim_to_first_right_slash "$source_suffix")")
     destination=$(trim_right_slash "$backup_path/$backup_path_suffix")
     [ -z "$dry_run" ] && create_directory "$destination" "$host" "$user" "$port"
+
+    if [ "$?" -ne "0" ]; then
+        echo "Could not not create directory ${destination}"
+        exit_code=10
+    fi
+
     source="$source_root/$source_suffix"
 
     if [ -z "$port" ]; then
         rsync -aE --protect-args --progress --delete $dry_run \
             --link-dest "$latest_link/$backup_path_suffix" \
             "$source" \
             "$remote_prefix$destination"
+
+        if [ "$?" -ne "0" ]; then
+            echo "Unable to backup ${source} to ${remote_prefix}${destination}"
+            exit_code=10
+        fi
     else
         rsync -aE --protect-args --progress --delete $dry_run --rsh="ssh -p $port" \
             --link-dest "$latest_link/$backup_path_suffix" \
             "$source" \
             "$remote_prefix$destination"
+
+        if [ "$?" -ne "0" ]; then
+            echo "Unable to backup ${source} to ${remote_prefix}${destination}"
+            exit_code=10
+        fi
     fi
 
     index=$((index + 1))
     source_path="$(dequote_string "$(get_list_item "$source_paths" "$index")")"
+    if [ "$?" -ne "0" ]; then
+        echo "Could not get source paths from ${source_paths}"
+        exit_code=15
+    fi
 done
 
+if [ "$exit_code" -ne "0" ]; then
+    exit $exit_code
+fi
+
 if [ -z "$dry_run" ]; then
     remove_path "$latest_link" "$host" "$user" "$port"
+    if [ "$?" -ne "0" ]; then
+        echo "Could not remove previous link to latest backup"
+        exit 20
+    fi
+
     create_link "$backup_path" "$latest_link" "$host" "$user" "$port"
+    if [ "$?" -ne "0" ]; then
+        echo "Could not link to latest backup"
+        exit 30
+    fi
 fi
-