bin/: Use explicit "--" separator for assert-arg usages

In order to prevent legitimate cases to fail as errors, such as:

  NUM='-10'
  eval "$(assert-arg "$NUM" '-n NUM')"

To prevent assert-arg(1) from treating "-10" as the options "-1 and -0,
they need to be put after the "--" separator.

This way, all usages of assert-arg(1) that had its first argument as a
variable were adapted, and the usage and examples of assert-arg itself
were updated to encourage this best practice.

1 files changed, 1 insertions, 1 deletions

diff --git a/bin/prompt b/bin/prompt
index 247c81a..382588d 100755
--- a/bin/prompt
+++ b/bin/prompt
@@ -64,7 +64,7 @@ done
 shift $((OPTIND - 1))
 
 STRING="${1:-}"
-eval "$(assert-arg "$STRING" 'STRING')"
+eval "$(assert-arg -- "$STRING" 'STRING')"
 
 printf '%s' "$STRING"
 printf ' [Y/n]: '