Index: build/utils/kitcreator-downloader.tcl
==================================================================
--- build/utils/kitcreator-downloader.tcl
+++ build/utils/kitcreator-downloader.tcl
@@ -1,49 +1,64 @@
 #!/usr/bin/env tclsh
-# KitCreator downloader v0.2.1 -- download Tclkits created with the KitCreator
-# Web Interface. Works with Tcl 8.5+ and Jim Tcl v0.75+.
+# KitCreator downloader v0.2.2 -- download Tclkits created with the KitCreator
+# Web Interface. Works with Tcl 8.5+ and Jim Tcl v0.75+. This script requires
+# that cURL be available through [exec curl].
 # Copyright (C) 2016, dbohdan.
 # License: MIT.
 proc download url {
-    # Guess at what the buildinfo URL might be if we are given, e.g., a building
-    # page URL.
-    set url [string map {/building {}} $url]
     if {![string match */buildinfo $url]} {
-        append url /buildinfo
+        # Guess at what the buildinfo URL might be if we are given, e.g., a
+        # building page URL.
+        set url [string map {/building {}} $url]
+        set checksum {}
+        foreach piece [split $url /] {
+            if {[regexp {^[a-z0-9]{40}$} $piece checksum]} {
+                break
+            }
+        }
+        if {$checksum eq {}} {
+            error "can't determine how to get the from the URL \"$url\" to the\
+                    buildinfo"
+        }
+        set url [regexp -inline "^.*$checksum" $url]/buildinfo
     }
 
     set buildInfo [exec curl -s $url]
 
     set filename [dict get $buildInfo filename]
     append filename -[dict get $buildInfo tcl_version]
     append filename -[dict get $buildInfo platform]
 
-    foreach option {staticpkgs threaded debug} {
-        if {[dict exists $buildInfo options $option] &&
-                [dict get $buildInfo options $option]} {
-            append filename -$option
-        }
-    }
-
-    append filename -[join [dict get $buildInfo packages] -]
+    if {[llength [dict get $buildInfo packages]] > 0} {
+        foreach option {staticpkgs threaded debug} {
+            if {[dict exists $buildInfo options $option] &&
+                    [dict get $buildInfo options $option]} {
+                append filename -$option
+            }
+        }
+        append filename -[join [dict get $buildInfo packages] -]
+    }
 
     set tail [file tail $url]
     # We can't use [file dirname] here because it will transform
-    # "http://example.com" into "http:/example.com".
+    # "http://example.com/" into "http:/example.com/".
     set baseUrl [string range $url 0 end-[string length $tail]]
     if {[string index $baseUrl end] ne {/}} {
         append baseUrl /
     }
     set tclkit $baseUrl[dict get $buildInfo filename]
 
     puts "Downloading $tclkit to $filename..."
     exec curl -o $filename $tclkit >@ stdout 2>@ stderr
-    file attributes $filename -permissions +x
+
+    catch {exec chmod +x $filename}
 }
 
 set url [lindex $argv 0]
 if {$url eq {}} {
     puts "usage: $argv0 url"
-    puts {The URL must be a KitCreator Web Interface buildinfo page.}
+    puts {The URL should be a KitCreator Web Interface buildinfo page.\
+            If it is instead, e.g., a building page or a direct Tclkit download\
+            URL, the script will try to guess where the buildinfo is.}
 } else {
     download $url
 }