py3: replace `time.clock()` with `time.perf_counter()` The former was removed in 3.8. The util function uses `time.clock()` if the latter is unavailable. Differential Revision: https://phab.mercurial-scm.org/D7779

tests: fix a "naked exception" issue in test-remotefilelog-prefetch.t Differential Revision: https://phab.mercurial-scm.org/D7811

subrepo: fix a crash when archiving an svn or git subrepo Only hgsubrepos have a repository attribute. This is pretty hacky, but probably the best we can do on stable. Pushing the lfstatus check down into the wrapper for hgsubrepo (and dropping the check for lfstatus at the top of `hgsubrepoarchive()`) resulted in various test failures because: 1) hgsubrepoarchive isn't returning the number of files archived at the bottom, resulting in an error about += NoneType 2) These copypasta archive wrappers don't use progress bars 3) Largefiles are *not* currently archived when using extdiff (68822b7cdd01), but pushing this context manager down into the subrepo resulted in it apparently doing so (as evidenced by progress bars being dropped) The other uses of `lfstatus()` are not in the substate processing loop, so they shouldn't be an issue. I initially put testcases in this test for largefiles-{on,off}, and it flagged a bunch of exit code differences for `cat` and `diff`, so I backed that off. Differential Revision: https://phab.mercurial-scm.org/D7714