Tracking issue for CommandExt::session_leader

[alexcrichton]

This is a tracking issue for the unstable process_session_leader feature in the standard library. Added in #26470 some open questions are:

• Is there a Windows "equivalent" that should mean this is exposed on Command directly?
• Is this the best name for the function? Should it just be called setsid?
• Is this best done through some different means? (e.g. a closure-after-fork approach)

cc @l0kod

[alexcrichton]

Nominating for discussion in 1.6

[alexcrichton]

After some discussion the libs team decided to punt this to another cycle.

[alexcrichton]

🔔 This issue is now entering its cycle-long final comment period for deprecation in 1.9 🔔

The libs team currently considers this implementable in terms of #31398, so that can likely suffice for now while we decide what set of these we want in the standard library.

[alexcrichton]

The libs team discussed this issue during triage yesterday and the conclusion was to deprecate