obshistory: add docstring to cmddebugobshistory Add debugobshistory command documentation based on the log command documentation.

obshashrangecache: make sure we re-warm the cache after a reset This will "mitigate" the effect of dropping existing entries when new markers affect existing range.

obshashrangecache: precisely track affected revs when adding new markers This will be useful when we start doing finer grained invalidation (instead of dropping all data).

debugobshistory: handle multiple cycles We previously handled up to one cycle only. This is now fixed.

test: clean the debugobshistory cycle test Use 'desc(...)' instead of revision numbers. Also blank lines between commands in the same test

obsdiscovery: add more debug output we add a summary debug output to help gathering data.