Frank Shearar uploaded a new version of Installer-Core to project The Trunk:
http://source.squeak.org/trunk/Installer-Core-fbs.369.mcz

==================== Summary ====================

Name: Installer-Core-fbs.369
Author: fbs
Time: 3 May 2013, 11:19:53.159 pm
UUID: 7956de6c-f92a-4830-bcc4-0cb2182ed4c5
Ancestors: Installer-Core-fbs.368

Dale Henrich stubbed his toe on this:

(Installer url: 'http://seaside.gemstone.com/ss/metacello')
    addPackage: 'ConfigurationOfMetacello-dhk.754.mcz';
    install.

results in the URL 'http://seaside.gemstone.com/ss/metacelloConfigurationOfMetacello-dhk.754.mcz' (note the missing / between 'metacello' and 'Configuration).

So when someone leaves off the /, and _specifies a package_, just insert a /.

=============== Diff against Installer-Core-fbs.368 ===============

Item was added:
+ ----- Method: InstallerUrl>>addPackage: (in category 'as yet unclassified') -----
+ addPackage: aPackageName
+ 	super addPackage: aPackageName.
+ 	(self url endsWith: '/') ifFalse: [self url: self url, '/'].!