Sorry... MacHg doesn't actually automatically support these extensions.
I'll mark this is I won't fix for now since I don't have any plans to support these. Also its pretty easy for users to enter these URI directly, and well unless its in core mercurial supporting all extensions is tricky. However if lots and lots of users really want this I would of course consider adding it.
Also if someone else wants to add this then I would be happy to accept the patches... ;)
I figured it would not be a priority, but since I noticed that you were starting to look at hgsubversion (and perhaps hg-git too?) I thought that there might be some way to have MacHG be able to use all such nonstandard URIs without doing something tied to a particular extension.
Yes you are totally correct that I am about to smooth out the experience when using the extensions for both svn, and git :) And yep you are also correct that these are in the same area and sort of related...
But, the thing I need to change for svn and git is the "discovery" code and through this the compatible repositories. Ie which repositories are "linked" to which other repositories... The other stuff sort of falls out automatically.
For these URI shortcut extensions, there is of course some lookup going on at the mercurial level. It wouldn't be too hard to make it work, one would basically
confirm that the schemes extension is active
then read the settings of showconfig for schemes.
Then substitute all schemes shortcuts found into the paths.default and paths.default-push URI's from showconfig.
Another question is after doing this once should MacHg check the hgrc of the repos at startup each time to try and catch if the user changes these settings? I would then see this as more tying MacHg configuration to the underlying hgrc settings here, and to a large degree for MacHg the configuration settings are currently nicely split between MacHg and the hgrc settings.
On the flip side, its *really* easy for users to just change the paths.default and paths.default-push to the full URI...
Moreover, there is enough confusion with users not being able to connect correctly to the right host, have the right ssh keys, or the correct https fingerprints or certificates, passwords, etc. That I sort of have a desire to remove as much complexity as I can from this mix...
But as I said I am happy to take patches for this feature :)
Personally I use hgbb rather than schemes (I like the "bbforks" command it gives you). I can understand that someone who interacts only through MacHG would not have as much need of these shortcuts as someone who mostly uses it non-day-to-day stuff.
I think what I would want to see would be just for them to show up in the push/pull dialogs as something that can be selected even if they do not show up anywhere else.
As for patches, the most experience I have with C type code is a dice roller :) ; however I am rather good at optimizing and cleaning up xcode builds if you want any help with that (I have not really looked at MacHG's project file yet).