Integration with vdirsyncer

This is an enhancement request:

• given that configuring two distinct programs is a mess for new users, resulting in lower khal adoption
• given that the vdirsyncer and khal authors seem to collaborate efficiently ;-)

I dream to see a better vdirsyncer/ikhal integration, such that:

• vdirsyncer is still an autonomous program (with a specific configuration file for autonomous use), but some of its functions are callable from ikhal,
• I only have to manage the khal configuration file, with vdirsyncer specific parameters inside,
• such parameters are transmitted by ikhal to vdirsyncer functions when needed,
• ikhal synchronize (with vdirsyncer functions) on start, may be ultimately in a separate thread to minimize start-up latency,
• when I type the '$' key (as with mutt) or when I quit ikhal, ikhal starts a (blocking) synchronization with vdirsyncer

Is my dream possible?

Start by reading the ikhal and vdirsyncer integration entry points; this issue names no files or tests. Determine how vdirsyncer functions could be configured through khal, synchronized at startup, and triggered by $ or quit. Done would require an agreed design and tests covering configuration and each synchronization trigger.