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
$ hg init t
$ cd t
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ echo This is file b1 > b
$ hg add b
$ hg commit -m "commit #1"
$ rm b
$ hg update 0
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo This is file b2 > b
$ hg add b
$ hg commit -m "commit #2"
created new head
$ cd ..; rm -r t
$ mkdir t
$ cd t
$ hg init
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ echo This is file b1 > b
$ hg add b
$ hg commit -m "commit #1"
$ rm b
$ hg update 0
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo This is file b2 > b
$ hg commit -A -m "commit #2"
adding b
created new head
$ cd ..; rm -r t
$ hg init t
$ cd t
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ echo This is file b1 > b
$ hg add b
$ hg commit -m "commit #1"
$ rm b
$ hg remove b
$ hg update 0
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo This is file b2 > b
$ hg commit -A -m "commit #2"
adding b
created new head
$ cd ..