transaction: avoid ambiguity of file stat at restoring from backup
In some cases below, copying from backup is used to restore original
contents of a file, which is backuped via addfilegenerator(). 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 (from '.hg/journal.backup.*')
- rollback of previous transaction (from '.hg/undo.backup.*')
To avoid ambiguity of file stat at restoring, this patch invokes
util.copyfile() with checkambig=True.
This patch is a part of "Exact Cache Validation Plan":
https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
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Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing:
$ make local # build for inplace usage
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See https://mercurial-scm.org/ for detailed installation
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