debugcommands: add support for extensions adding their own debug info...
debugcommands: add support for extensions adding their own debug info
We've had a couple of cases where it'd be handy at Google to add data
to `hg debuginstall`'s output. We've kludged around that at various
times, but it seems reasonable to let extensions add their own data
here so extension maintainers can get useful extra data.
Differential Revision:
https://phab.mercurial-scm.org/D6681