scmutil: add file object wrapper class to check ambiguity at closing
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 adds file object wrapper class checkambigatclosing to check
(and get rid of) ambiguity at closing. It is used by vfs in subsequent
patch.
This is a part of ExactCacheValidationPlan.
https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan
BTW, checkambigatclosing is tested in test-filecache.py, even though
it doesn't use filecache itself, because filecache assumes that file
stat ambiguity never occurs (and there is no another test-*.py related
to filecache).
#require docutils
#require gettext
Test document extraction
$ HGENCODING=UTF-8
$ export HGENCODING
$ { echo C; ls "$TESTDIR/../i18n"/*.po | sort; } | while read PO; do
> LOCALE=`basename "$PO" .po`
> echo "% extracting documentation from $LOCALE"
> LANGUAGE=$LOCALE python "$TESTDIR/../doc/gendoc.py" >> gendoc-$LOCALE.txt 2> /dev/null || exit
>
> if [ $LOCALE != C ]; then
> if [ ! -f $TESTDIR/test-gendoc-$LOCALE.t ]; then
> echo missing test-gendoc-$LOCALE.t
> fi
> cmp -s gendoc-C.txt gendoc-$LOCALE.txt && echo "** NOTHING TRANSLATED ($LOCALE) **"
> fi
> done; true
% extracting documentation from C
% extracting documentation from da
% extracting documentation from de
% extracting documentation from el
% extracting documentation from fr
% extracting documentation from it
% extracting documentation from ja
% extracting documentation from pt_BR
% extracting documentation from ro
% extracting documentation from ru
% extracting documentation from sv
% extracting documentation from zh_CN
% extracting documentation from zh_TW