performance: do not stat() things when not required
Ignore unknown files if we don't need them (eg in hg diff).
It slows things down a little bit for big trees (kernel repo), since _join()
is called for each file instead of for each directory.
fix issue567
adding bar
adding foo
adding quux1
adding quux2
created new head
merging bar
merging bar failed!
merging foo and baz to baz
1 files updated, 1 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
U bar
R baz
3 files updated, 0 files merged, 1 files removed, 0 files unresolved
merging bar
merging bar failed!
merging baz and foo to baz
1 files updated, 1 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
% show unresolved
U bar
R baz
% unmark baz
% show
U bar
U baz
% re-resolve baz
merging baz and foo to baz
% after
U bar
R baz
% resolve all
merging bar
warning: conflicts during merge.
merging bar failed!
% after
U bar
R baz