dirstate: stop gathering parentfiledata in update_file
Gathering information here assume that they are valid cache information for a
clean file. It is true most of the time, but not garanteed.
Accurate data can still be explicitly provided.
We drop the spontaneous and will let the next `hg status` call record actual information.
Differential Revision: https://phab.mercurial-scm.org/D11791
Test issue2761
$ hg init
$ touch to-be-deleted
$ hg add
adding to-be-deleted
$ hg ci -m first
$ echo a > to-be-deleted
$ hg ci -m second
$ rm to-be-deleted
$ hg diff -r 0
Same issue, different code path
$ hg up -C
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ touch does-not-exist-in-1
$ hg add
adding does-not-exist-in-1
$ hg ci -m third
$ rm does-not-exist-in-1
$ hg diff -r 1