Double-authentication causes installation failure.

[andymatuschak]

**Andy Matuschak (andymatuschak)* reported (on Launchpad) on' 2008-05-09:*

1. Try to update an app without write access.
2. Get authentication prompt; cancel.
3. Check for updates again and authorize this time.
4. Note that Sparkle fails to copy the new app in place but still trashes the old one.

[andymatuschak]

**Catfish_Man (catfish-man)* wrote on 2008-05-14:*

I think this may be due to OSX auto-renaming duplicate files as they're
put into NSTemporaryDirectory. I had updates with 1-5 appended to the
name after some failed testing.

[andymatuschak]

**Andy Matuschak (andymatuschak)* wrote on 2008-05-14:*

Sparkle actually does the auto-renaming bit. It's in
[SUBasicUpdateDriver download:decideDestinationWithSuggestedFilename:]

[andymatuschak]

**Andy Matuschak (andymatuschak)* wrote on 2008-06-28:*

I still can't for the life of me figure out why this happens.
Security.framework is inscrutable.