vfs: use checkambigatclosing in checkambig=True but atomictemp=False case
In Mercurial source tree, opening a file in "a"/"a+" mode like below
doesn't specify atomictemp=True for vfs, and this avoids file stat
ambiguity check by atomictempfile.
- writing changes out in revlog layer uses "a+" mode
- truncation in repair.strip() uses "a" mode
- truncation in transaction._playback() uses "a" mode
If steps below occurs at "the same time in sec", all of mtime, ctime
and size are same between (1) and (3).
1. append data to revlog-style file (and close transaction)
2. discard appended data by truncation (strip or rollback)
3. append same size but different data to revlog-style file again
Therefore, cache validation doesn't work after (3) as expected.
This patch uses checkambigatclosing in checkambig=True but
atomictemp=False case, to check (and get rid of) file stat ambiguity
at closing.
This is a part of ExactCacheValidationPlan.
https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan
$ hg init
$ echo This is file a1 > a
$ echo This is file b1 > b
$ hg add a b
$ hg commit -m "commit #0"
$ echo This is file b22 > b
$ hg commit -m "comment #1"
$ hg update 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm b
$ hg commit -A -m "comment #2"
removing b
created new head
$ hg update 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ rm b
$ hg update -c 2
abort: uncommitted changes
[255]
$ hg revert b
$ hg update -c 2
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ mv a c
Should abort:
$ hg update 1
abort: uncommitted changes
(commit or update --clean to discard changes)
[255]
$ mv c a
Should succeed:
$ hg update 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved