Update to shellcheck-0.8.0

v0.8.0 - 2021-11-06
Added
* disable=all now conveniently disables all warnings
* external-sources=true directive can be added to .shellcheckrc to make
  shellcheck behave as if -x was specified.
* Optional check-extra-masked-returns for pointing out commands with
  suppressed exit codes (SC2312).
* Optional require-double-brackets for recommending [[ ]] (SC2292).
* SC2286-SC2288: Warn when command name ends in a symbol like /.)'"
* SC2289: Warn when command name contains tabs or linefeeds
* SC2291: Warn about repeated unquoted spaces between words in echo
* SC2292: Suggest [[ over [ in Bash/Ksh scripts (optional)
* SC2293/SC2294: Warn when calling eval with arrays
* SC2295: Warn about "\({x#\)y}" treating $y as a pattern when not quoted
* SC2296-SC2301: Improved warnings for bad parameter expansions
* SC2302/SC2303: Warn about loops over array values when using them as keys
* SC2304-SC2306: Warn about unquoted globs in expr arguments
* SC2307: Warn about insufficient number of arguments to expr
* SC2308: Suggest other approaches for non-standard expr extensions
* SC2313: Warn about read with unquoted, array indexed variable

Fixed
* SC2102 about repetitions in ranges no longer triggers on [[ -v arr[xx] ]]
* SC2155 now recognizes typeset and local read-only declare statements
* SC2181 now tries to avoid triggering for error handling functions
* SC2290: Warn about misused = in declare & co, which were not caught by
  SC2270+
* The flag --color=auto no longer outputs color when TERM is "dumb" or
  unset

Changed
* SC2048: Warning about $* now also applies to ${array[*]}
* SC2181 now only triggers on single condition tests like [ $? = 0 ].
* Quote warnings are now emitted for declaration utilities in sh
* Leading _ can now be used to suppress warnings about unused variables
* TTY output now includes warning level in text as well as color

Removed
* SC1004: Literal backslash+linefeed in '' was found to be usually correct

(pho)