Add bash version requirements for certain functions

Makefile

@@ -1,5 +1,5 @@
 MAJOR_VERSION=1
-VERSION=1.20
+VERSION=1.21
 
 TARGET := bash-boost-$(VERSION)
 SRCS := $(shell find src -type f -name "*.sh" | sort)

docgen

@@ -54,6 +54,9 @@ sub formatmd {
         elsif (my ($v) = ($text =~ m/^\s*\@returns:\s*(.*)$/)) {
            print "\n**Returns:** $v\n"; 
         }
+        elsif (($v) = ($text =~ m/^\s*\@requires:\s*(.*)$/)) {
+           print "\n**Requires:** bash $v or later\n";
+        }
         elsif ($text =~ m/^\s*\@notes:/) {
            print "\n**Notes:**\n\n";
         }

src/MANUAL.md

@@ -1,7 +1,7 @@
 ---
 title: BASH-BOOST(1)
 author: github.com/tomocafe
-date: August 11, 2024
+date: September 9, 2024
 ---
 
 
@@ -1133,6 +1133,8 @@ func() {
 
 Unpacks list items into named variables
 
+**Requires:** bash 4.3 or later
+
 **Arguments:**
 
 - `LISTVAR`: name of the list variable (do not include $)
@@ -1142,6 +1144,8 @@ Unpacks list items into named variables
 
 Maps a function over a list, modifying it in place
 
+**Requires:** bash 4.3 or later
+
 **Arguments:**
 
 - `LISTVAR`: name of the list variable (do not include $)
@@ -1151,6 +1155,8 @@ Maps a function over a list, modifying it in place
 
 Maps a function over a list of keys to generate an associative array
 
+**Requires:** bash 4.3 or later
+
 **Arguments:**
 
 - `LISTVAR`: name of an associative array variable (do not include $)

src/core/core.sh

@@ -165,3 +165,13 @@ function bb_cleanup () {
     done < <(set -o posix; set)
     : # don't use return "$__bb_true" here, it's now undefined
 }
+
+function _bb_checkbashversion () {
+    [[ ${BASH_VERSINFO[0]} -lt ${1:-0} ]] && return $__bb_false
+    [[ ${BASH_VERSINFO[0]} -eq ${1:-0} && ${BASH_VERSINFO[1]} -lt ${2:-0} ]] && return $__bb_false
+    return $__bb_true
+}
+
+function _bb_unsupportedbashversion () {
+    echo "$1: requires bash ${2:-0}.${3:-0} or later (detected $BASH_VERSION)" 1>&2
+}