py3: make contrib/revsetbenchmarks.py not import symbols from stdlib modules

py3: make contrib/bdiff-torture.py conform to our import style

import-checker: extend check of symbol-import order to all local modules It doesn't make sense that (a) is allowed whereas (b) is disallowed. a) from mercurial import hg from mercurial.i18n import _ b) from . import hg from .i18n import _

import-checker: always build a list of imported symbols The next patch will rely on it.

import-checker: fix test to make a real package Otherwise "testpackage" wouldn't be counted as a package when building a list of imported symbols.

py3: move up symbol imports to enforce import-checker rules Since (b) is banned, we should do the same for (a) for consistency. a) from mercurial import hg from mercurial.i18n import _ b) from . import hg from .i18n import _

util: make copyfile avoid ambiguity of file stat if needed In some cases below, copying from backup is used to restore original contents of a file. If copying keeps ctime, mtime and size of a file, restoring is overlooked, and old contents cached before restoring isn't invalidated as expected. - failure of transaction before closing (from '.hg/journal.backup.*') - rollback of previous transaction (from '.hg/undo.backup.*') To avoid such problem, this patch makes copyfile() avoid ambiguity of file stat, if needed. Ambiguity check is executed, only if: - checkambig=True is specified (not all copying needs ambiguity check), and - destination file exists before copying This patch also adds 'not (copystat and checkambig)' assertion, because combination of copystat and checkambig is meaningless. This patch is a part of preparation for "Exact Cache Validation Plan": https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan

vfs: make rename avoid ambiguity of file stat if needed In some cases below, renaming from backup is used to restore original contents of a file. If renaming keeps ctime, mtime and size of a file, restoring is overlooked, and old contents cached before restoring isn't invalidated as expected. - failure of transaction before closing (only from '.hg/journal.dirstate') - rollback of previous transaction (from '.hg/undo.*') - failure in dirstateguard scope (from '.hg/dirstate.SUFFIX') To avoid such problem, this patch makes vfs.rename() avoid ambiguity of file stat, if needed. Ambiguity check is executed, only if: - checkambig=True is specified (not all renaming needs ambiguity check), and - destination file exists before renaming This patch is a part of preparation for "Exact Cache Validation Plan": https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan

vfs: make atomictempfile avoid ambiguity of file stat if needed This patch is a part of preparation for "Exact Cache Validation Plan": https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan

util: make atomictempfile avoid ambiguity of file stat if needed Ambiguity check is executed at close(), only if: - atomictempfile is created with checkambig=True, and - target file exists before renaming This restriction avoids performance decrement by needless examination of file stat (for example, filelog doesn't need exact cache validation, even though it uses atomictempfile to write changes out). See description of filestat class for detail about why the logic in this patch works as expected. This patch is a part of preparation for "Exact Cache Validation Plan": https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan