gsu: Improve documentation of gsu_getopts().

The sentence which explains how $o_X is set for both types of options
was rather confusing. The new text should be better.

While we're at it,
	* mention that getopts is a bash builtin
	* switch to "modern" ((expr)) arithmetic evaluation in example
	* use '' to quote constants in example

diff --git a/misc/gsu/subcommand b/misc/gsu/subcommand
index 4e363628adb29185fd6857a9fc50caf5a1fddada..3a1bc6db6697c7a0676a45ae940b930d18ee8901 100644 (file)
--- a/misc/gsu/subcommand
+++ b/misc/gsu/subcommand
@@ -308,21 +308,20 @@ complete_help()
        echo "$result"
 }
 
-# Wrapper for bash's getopts.
+# Wrapper for the bash getopts builtin.
 #
 # Aborts on programming errors such as missing or invalid option string.  On
 # success $result contains shell code that can be eval'ed. For each defined
 # option x, the local variable o_x will be created when calling eval "$result".
-# o_x contains true/false for options without an argument or the emtpy string/the
-# given argument, depending on whether this option was contained in the "$@"
-# array.
+# o_x contains true/false for options without argument and either the emtpy
+# string or the given argument for options that take an argument.
 #
 # Example:
 #      gsu_getopts abc:x:y
 #      eval "$result"
-#      [[ $ret -lt 0 ]] && return
+#      (($ret < 0)) && return
 #
-#      [[ "$o_a" = "true ]] && echo "The -a flag was given"
+#      [[ "$o_a" = 'true' ]] && echo 'The -a flag was given'
 #      [[ -n "$o_c" ]] && echo "The -c option was given with arg $o_c"
 gsu_getopts()
 {