test-subrepo: glob away an unstable hash This is the instability mentioned at the beginning of the series. I don't like hiding it, but I don't want to sit on a fix for a user reported problem while trying to figure this out. The instability seems related to the cset with a .hgsub with a remote URL. (There's very little existing remote URL subrepo testing.)

subrepo: activate clone pooling to enable sharing with remote URLs This is the easiest way to ensure that repositories with remote subrepo references can share the subrepos, consistent with how local subrepos can be shared.

subrepo: don't attempt to share remote sources (issue5793) Untangling _abssource() to resolve the new subrepo relative to the shared parent's share path, and then either sharing from there (if it exists), or cloning to that location and then sharing, is probably more than should be attempted on stable. Absolute subrepo references are discouraged, so for now, this resumes the behavior prior to 68e0bcb90357 of cloning the absolute subrepo locally.

test-subrepo: demonstrate problems with subrepo sharing and absolute paths This affects remote paths in .hgsub, as well as clone pooling from a remote source. For reasons unknown, there are stability issues with the relative-path.t tests. If run as a single test, it is stable. If run with --loop, or with -jX for X>1, the hash of the parent repo changes. I'm seeing this on both Windows and Fedora 26. I added an `hg log --debug`, and the manifest hash changes, but I have no idea why.