[MacPorts] #64050: sync over git: rebase with autostash only if fast-forwarding fails

[MacPorts]

#64050: sync over git: rebase with autostash only if fast-forwarding fails
--------------------------+--------------------
 Reporter:  chrstphrchvz  |      Owner:  (none)
     Type:  enhancement   |     Status:  new
 Priority:  Normal        |  Milestone:
Component:  base          |    Version:  2.7.1
 Keywords:                |       Port:
--------------------------+--------------------
 I sync the ports tree from GitHub (wiki:howto/SyncingWithGit). By default,
 `port sync` relies on `git pull --rebase --autostash`, which touches every
 uncommitted file—even when a fast-forward is possible. This causes ports
 with local changes to be reparsed even if no remote changes were made.

 Maybe my workflow is not very good, but I tend to have a lot of
 uncommitted/unmerged changes, and I believe it would be nice if `port
 sync` tried to fast-forward before trying to rebase with autostash, so
 that parsing ports can take seconds rather than minutes to complete.

 I think this should be possible, but to my knowledge `git pull` doesn’t
 have an option to try fast forwarding before rebasing with autostash using
 a single command, and so the trick seems to be figuring out how to do so
 using exactly one command for `macports::GetVCSUpdateCmd` to return. Maybe
 put it all in a string for `bash -c`?

-- 
Ticket URL: <https://trac.macports.org/ticket/64050>
MacPorts <https://www.macports.org/>
Ports system for macOS