(pre_sync): Store the previous backup file.
(copy_file): Abort if we cannot seek or read the file we copy from. Abort if the value we read didn't end in a newline, start with "T ", "C " or "P ", if the identity number in the data isn't what we expected, or if it isn't followed by a space. This change attempts to detect file damage as early as possible.
Showing with 68 additions and 9 deletions