demandimport: ignore pwd and grp.
Both are unavailable under Windows and tarfile detects them via ImportError.
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
pulling from ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
merging testdir/subdir/a and testdir/a
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
M testdir/subdir/a
diff -r d02b3fc32762 testdir/subdir/a
--- a/testdir/subdir/a
+++ b/testdir/subdir/a
@@ -1,1 +1,1 @@ a
-a
+alpha