tests: clean up a newly-introduced instance of `python` Differential Revision: https://phab.mercurial-scm.org/D16

tests: clean up even more direct `python` calls with $PYTHON This time ones that are prefixed with =, ", ', or `. This appears to be the last of them. Differential Revision: https://phab.mercurial-scm.org/D14

contrib: widen the "don't use `python`" net a little I'm still cleaning this up, but it's easier to do in bite-size chunks like this than all at once. The negative lookahead avoids one false positive category from some output related to finding Subversion bindings. Differential Revision: https://phab.mercurial-scm.org/D13

followlines: join merge parents line ranges in blockdescendants() (issue5595) In blockdescendants(), we had an assertion when line range of a merge changeset was not consistent depending on which parent was considered for computation. For instance, this might occur when file content (in lookup range) is significantly different between parent branches of the merge as demonstrated in added tests (where we almost completely rewrite the "baz" file while also introducing similarities with its content in the other branch we later merge to). Now, in such case, we combine line ranges from all parents by storing the envelope of both line ranges. This is conservative (the line range is extended, possibly unnecessarily) but at least this should avoid missing descendants with changes in a range that would fall in that of one parent but not in another one (the case of "baz: narrow change (2->2+)" changeset in tests).

workingfilectx: add exists, lexists Switch the lone call in merge.py to use it. As with past refactors, the goal is to make wctx hot-swappable with an in-memory context in the future. This change should be a no-op today.

vfs: add explanation about cost of checkambig=True in corner case

vfs: replace avoiding ambiguity in abstractvfs.rename with _avoidambig This centralizes common logic to forcibly avoid file stat ambiguity into _avoidambig(), which was introduced by previous patch.

vfs: copy if EPERM to avoid file stat ambiguity forcibly at closing Now, files (to be truncated) are opened with checkambig=True, only if localrepository caches it. Therefore, straightforward "copy if EPERM" is always reasonable to avoid file stat ambiguity at closing. This patch makes checkambigatclosing close wrapper copy the target file, and advance mtime on it after renaming, if EPERM. This can avoid file stat ambiguity, even if the target file is owned by another (see issue5418 and issue5584 for detail). This patch factors main logic out instead of changing checkambigatclosing._checkambig() directly, in order to reuse it.

transaction: apply checkambig=True only on limited files for similarity Now, transaction can determine whether avoidance of file stat ambiguity is needed for each files, by blacklist "checkambigfiles". For similarity to truncation in _playback(), this patch apply checkambig=True only on limited files in code paths below. - restoring files by util.copyfile(), in _playback() (checkambigfiles itself is examined at first, because it as a keyword argument might be None) - writing files at finalization of transaction, in _generatefiles() This patch reduces cost of checking stat at writing out and restoring files, which aren't filecache-ed.

transaction: avoid file stat ambiguity only for files in blacklist Advancing mtime by os.utime() fails for EPERM, if the target file is owned by another. bff5ccbe5ead and related changes made some code paths give advancing mtime up in such case, to fix issue5418. This causes file stat ambiguity (again), if it is owned by another. https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan To avoid file stat ambiguity in such case, especially for .hg/dirstate, ed66ec39933f made vfs.rename() copy the target file, and advance mtime of renamed one again, if EPERM (see issue5584 for detail). But straightforward "copy if EPERM" isn't reasonable for truncation of append-only files at rollbacking, because rollbacking might cost much for truncation of many filelogs, even though filelogs aren't filecache-ed. Therefore, this patch introduces blacklist "checkambigfiles", and avoids file stat ambiguity only for files specified in this blacklist. This patch consists of two parts below, which should be applied at once in order to avoid regression. - specify 'checkambig=True' at vfs.open(mode='a') in _playback() according to checkambigfiles - invoke _playback() with checkambigfiles - add transaction.__init__() checkambigfiles argument, for _abort() - make localrepo instantiate transaction with _cachedfiles - add rollback() checkambigfiles argument, for "hg rollback/recover" - make localrepo invoke rollback() with _cachedfiles After this patch, straightforward "copy if EPERM" will be reasonable at closing the file opened with checkambig=True, because this policy is applied only on files, which are listed in blacklist "checkambigfiles".