world management and patches

["Daniel L. Weinreb" <DLW@alderaan.scrc.symbolics.com>]

    Date: Mon, 20 Jun 88 12:15 EDT
    From: barmar@Think.COM (Barry Margolin)

    What I need is a way to put these patches somewhere and tell the system
    "if anyone loads the C system, and the version number is less than
    XX.YY, AUTOMATICALLY load these patches afterward."

You say that your worlds are configured to load certain patches
automatically when they boot.  Can't you just extend this mechanism to
have them do the equivalent of ":Load Patches Color" when the Color
system is loaded?  Then just put the patches somewhere on disk such
that their logical pathnames map to that place, and the patches will
get loaded.  Your extension could either only be present in Color
worlds, or it could be present in all worlds and check at runtime
for the presence of Color, using sct:get-system-version.

(By the way, the reason that default system doesn't load patches
automatically is that there are occasionally times when you actually
don't want all the latest patches.  Suppose you're trying to reproduce a
bug that you suspect is fixed by a future patch, or suppose someone
accidentally makes a patch that breaks things and you know it and want
to avoid loading the bad patch.  Whether to load patches automatically
is considered a policy decision that the site maintainer has to make.)