• #817: Add a "--max-duration" flag to the "check" action and a "max_duration" option to the
  repository check configuration. This tells Borg to interrupt a repository check after a certain
  duration.
• #860: Fix interaction between environment variable interpolation in constants and shell escaping.
• #863: When color output is disabled (explicitly or implicitly), don't prefix each log line with
  the log level.
• #865: Add an "upload_buffer_size" option to set the size of the upload buffer used in "create"
  action.
• #866: Fix "Argument list too long" error in the "spot" check when checking hundreds of thousands
  of files at once.
• #874: Add the configured repository label as "repository_label" to the interpolated variables
  passed to before/after command hooks.
• #881: Fix "Unrecognized argument" error when the same value is used with different command-line
  flags.
• In the "spot" check, don't try to hash symlinked directories.