Detect OS upgrades and refer users to Migration

[Joshua Root]

On 2013-11-5 12:06 , Ryan Schmidt wrote:
> With Mavericks, more so than with previous OS versions (I think one reason is the different handling of .la files), users are running into errors when they selfupdate and upgrade outdated ports without realizing that we’d really prefer them to uninstall and reinstall all ports.
> 
> Is there a way that we could detect that the OS has been upgraded so that we could refer users to the Migration wiki page? I don’t think we keep track of the last-used OS X version anywhere, but maybe it’s as simple as checking if any installed port was installed for a different OS version than the current one (e.g. we’re now on darwin 13 but there are ports installed with darwin 12).

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