hghave: add "absimport" feature to check "absolute_import" in __future__ This patch adds "absimport" feature to check whether "absolute_import" exists in __future__, which means supporting module loading by absolute name. This check is needed for portability of test code using "absolute_import", because Python earlier than 2.5 doesn't support it.

merge: exit early during a no-op update (BC) hg update . (or equivalents) are effectively no-ops in just about all circumstances. These sorts of updates can be especially common in a bookmark-oriented workflow. This saves us a status check and a manifest decompression, which means that on a repo with over 210,000 files, this brings hg update . down from 2.5 seconds to 0.15. There is one change in behavior: a file that was added, not committed, and then deleted but not removed used to be removed from the dirstate. With this patch it isn't. This is what causes the change in test-mq-qpush-exact.t. This seems like it's enough of an edge case to not be worth handling. The output of test-empty.t changes because those files are not yet created.

localrepo: invoke only feature setup functions for enabled extensions Before this patch, each feature setup functions for localrepository class should examine whether corresponding extension is enabled or not by themselves. This patch invokes only feature setup functions defined in module of enabled extensions, and it makes implementation of feature setup functions easier and simpler.

lock: handle race in trylock/testlock on Windows readlock may raise IOError if the system does not support symlink.