The set builtin accepts certain flags, and some longer synonyms (for
instance set -e is the same as set -o errexit) under POSIX sh. This
makes ShellCheck warn if any of the used flags and options are
undefined when targeting POSIX sh.
This fixes#990, while adding general flag-support checking for set in
the process.
Flags for the hash builtin other than [-r] are undefined under POSIX sh.
Dash also accepts [-v], while bash adds [-l] [-p filename] [-dt] aside
from [-r].
Issue https://github.com/koalaman/shellcheck/issues/1330
Addresses false positives when quoted arguments to echo begin with what
looks like a flag. Now, warn only when the first argument is a
recognized echo flag when flags are unsupported.
The only acceptable flags for the unset builtin under POSIX sh and dash
are [-fv]. Bash though, accepts [-n] too. This commits makes shellcheck
warn about this.
There are no flags for the type builtin defined under POSIX sh, nor does
dash define any. Bash, however, allows [-aftpP]. We check this now under
POSIX and dash.
