[GSoC] migration

[Bradley Giesbrecht]

> On Sep 8, 2017, at 5:04 PM, Umesh Singla <umeshksingla at macports.org> wrote:
> 
> On Sat, Sep 9, 2017 at 3:40 AM, Rainer Müller <raimue at macports.org> wrote:
> On 2017-09-08 23:33, Umesh Singla wrote:
> > When I run the `migrate` action with only one port (expat) installed, I
> > get the following:
> >
> > $ sudo ./bin/port migrate
> >
> > Taking a snapshot of the current state...
> >
> > Done: Snapshot '8':'snapshot created for migration' created at
> > 2017-09-08 21:09:21
> >
> > Migration will first uninstall all the installed ports, upgrade MacPorts
> > and then reinstall them again. Would you like to continue? [Y/n]: Y
> 
> I would like to repeat that upgrading MacPorts from the 'port migrate'
> action is not possible. After a major upgrade of macOS we cannot
> guarantee that the old version of MacPorts runs at all on this new OS
> version. MacPorts has to be reinstalled for the new OS version in an
> extra step before.
> 
> The best you can do is printing instructions on where to download MacPorts.
> 
> So, what could be the possible two-stage break of migrate action be? I'm guessing immediately after uninstalling and selfupdating, I can print on the console asking the user to run `port restore --last` in order to complete migration. This command will now use the upgraded port command. Any suggestions?

If port cannot spawn this command then this should be a workable solution.

—
Brad