autosync and memorized sync settings

[mitsuhiko]

add and remove should automatically sync optionally. That however also means that sync needs a mode to sync with the last settings. I can imagine two options here:

1. sync always auto remembers and you need to set --reset to forget previous settings
2. sync gets a new flag --recall to recall previous sync settings, autosync would use this.

The following settings should be reused in either case

• pre
• features
• all-features
• with-sources

[mitsuhiko]

I tried both now and I prefer --reset. Makes autosync less confusing.