sudo mv /usr/local ~/local
then merge it back in
ditto -V ~/local /usr/local
That way it should merge all the files from the backup into the new folder (and show you what it's doing)
Thank you Apple. I think nobody will ever beat this time!!! Not even windows v100!!! I think I'll go for the Guiness Record...
Line 128,493 - INSTALLER LOG SHARED BUFFER IS FUL
This time I only opened the log viewer briefly at one point during the upgrade, and again after several hours because it seemed to have hung again. I can't imagine I'm the only one who's affected by this issue. I'll report back when/if I find out how to fix it.
In the meantime I've restarted the process one more time. The laptop still boots straight into the Yosemite installer so I don't think the hard reboots have adversely affected the machine.
edit: It occurs to me that the longest I've waited has been 12 hours (my first attempt). I've now seen reports of 15 hour installs, perhaps I didn't wait long enough? Even if the log buffer is full, that wouldn't necessarily mean that install has outright failed... hmm
$ find /usr/local | wc -l
$ du -sh /usr/local
Other than that, the upgrade was very smooth. Thanks for the help!