some-function () {
  { local -; set -x; } 2>/dev/null
   some-command "$@"
}

{ local -; set -x; } 2>/dev/null enables set -x (command tracing/xtrace) for just this function, without leaking that setting to the caller.

As a result, some-command "$@" runs with full -x tracing visible (since the redirect only applies to the group, not to the rest of the function), and the moment the function returns, xtrace (and any other option) reverts to whatever the caller had. The debug tracing is scoped to just this one function, with no side effects on the rest of the script.

Breaking it down:

• local -: local inside a function, given just -, saves the current shell option flags (everything set -o would show) into a function-local scope. When the function returns, bash restores the shell options to whatever they were before the function was called. - is treated as a special variable name by local specifically for this purpose.

• set -x: turns on xtrace, so every command executed afterward gets printed to stderr prefixed with +, showing exactly what’s running with expanded variables. This is normally a global, persistent setting.

• { ... } 2>/dev/null: the group command wraps both statements so the 2>/dev/null applies to both. This suppresses the trace output that set -x itself would otherwise immediately produce (bash echoes the set -x command’s own invocation), and suppresses any noise from local -. Without this redirect we would see stray + local - / + set -x lines in stderr before our actual tracing starts.