Heya,

Have spent cycles on this on-and-off these past few months; finally have
something worth discussing, I think 🤞

To recap where we stand, AFAIU: the reported vc-dir bug has been fixed
(in time for the emacs-30 branch), but the changes could feel intrusive,
since a new vc-dir header was added ("Tracking") that some users may not
care for.

I've now drafted a user option to give users more control over this new
header; see patch #3 in the attached series.

The first two patches are yak-shaving: patch #1 adds regression tests,
patch #2 splits vc-git-dir-extra-headers into more manageable chunks
(pure refactoring, no functional change intended).

Also attaching a 'squashed.patch' if that helps review.

About patch #2, CC'ing Sean Whitton for perspective on
vc-git--cmds-in-progress: I was puzzled by the function supporting many
commands (rebase, am, merge, bisect), whereas AFAICT its sole user only
heeds 'bisect & 'rebase.  Wondering if I've missed other in-tree uses,
or if we should add headers for 'am and 'merge, "while in there".

Curious what y'all think.  OT1H not sure an alist is the best UX, OTOH
struggled to keep option names concise otherwise.