This appears to be fixed now in the default branch (changeset f90d5641c78b).

Adding piranha and brodie, maybe they have opinions.

I've been experiencing this bug as well.  I applied the patch mentioned and 
it works.  Any chance this or something like it can get included in the next 
release?

Have cleaned up the patch, and will submit it to mercurial-devel.  Cheers
for the pointer.

Please send all patches to the -devel list.

Here's a better fix for the problem.  It checks for the specific case where
a local repo is specified using a scheme which doesn't look like a file://
scheme (i.e., from the schemes extension) and skips the abspath() step.

I'm not convinced the problem you mention would actually be a problem.  To
even find the repo you're cloning using the scheme extension, you must have
it enabled and be using a scheme that points to the right repo.  Unless you
explicitly change that setup after cloning, what could go wrong?

Also, turning the repo path into a 'correct' local path defeats one of the
use cases for schemes: namely, the ability for an admin to alias the
location of a central bunch of local repos, so that if (for whatever reason)
they need to be moved, it can be done just by changing the (globally
defined) scheme, and users don't notice any difference.

One potential problem is that the schemes extension might be enabled in the 
source repository local configuration, and thus the cloned repo will have an 
invalid default path. There could be other problems with relative paths not 
being resolved etc.

A better solution might be to just produce a correct local path instead.

There's a problem when cloning from a repo specified using the 'schemes'
extension.  If the scheme is a local file, the 'default' path in the clone's
.hg/hgrc is set incorrectly.  For example, suppose this is the setup in your
hgrc:

[extensions]
schemes = 

[schemes]
main = /path/to/repodirs

Running the command 'hg clone main://myrepo' from directory '/home/glenn'
(assuming myrepo exists in repodirs) results in a cloned repo with the
default path set to '/home/glenn:/myrepo' instead of 'main://myrepo' as
expected.

I've attached a patch which fixes this problem (but not entirely sure it
doesn't introduce others).