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/volume b/bin/volume
index 991fbc7..9056760 100755
--- a/bin/volume
+++ b/bin/volume
@@ -74,7 +74,7 @@ done
 shift $((OPTIND - 1))
 ACTION="${1:-}"
 
-eval "$(assert-arg "$ACTION" 'ACTION')"
+eval "$(assert-arg -- "$ACTION" 'ACTION')"
 
 
 rotate() {