grep: search working directory files by default if --all-files is specified
The default was -rtip:0 before, but "--all-files -rtip:0" would be the most
useless combination, and it isn't supported yet. Let's change the default to
something useful.
This isn't flagged as BC since --all-files isn't released.
Differential Revision: https://phab.mercurial-scm.org/D3917
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