subrepo: add the parent context to hgsubrepo This brings parity with gitsubrepo and svnsubrepo (which already reference their parent), and will be used in an upcoming patch. I'm a bit concerned that the parent context could get stale (consider what happens when the parent repo is reverted for example). I tried adding the parent context to the substate tuple so that the parent is available everywhere a state change is possible, but that made submerge() unhappy. Even with removing the parent context inside submerge(), I wasn't able to get all of the test diffs fixed. But since the other subrepos reference their parent too, if there is a problem, it is a preexisting one (that nobody seems to be running into). It can be fixed if/when it pops up.

fileset: add a fileset for portable filenames This has mostly the same semantics as the files that the 'ui.portablefilenames' config option would warn or abort about. The only difference is filenames that case-fold to the same string -- given a set of filenames we've already checked we can check whether a new one collides with them, but we don't have a way to tell which filename it collided with.