$ cat > writepatterns.py <<EOF

  > import sys

  > 

  > path = sys.argv[1]

  > patterns = sys.argv[2:]

  > 

  > fp = file(path, 'wb')

  > for pattern in patterns:

  >     count = int(pattern[0:-1])

  >     char = pattern[-1] + '\n'

  >     fp.write(char*count)

  > fp.close()

  > EOF

prepare repo

  $ hg init a

  $ cd a

These initial lines of Xs were not in the original file used to generate

the patch.  So all the patch hunks need to be applied to a constant offset

within this file.  If the offset isn't tracked then the hunks can be

applied to the wrong lines of this file.

  $ python ../writepatterns.py a 34X 10A 1B 10A 1C 10A 1B 10A 1D 10A 1B 10A 1E 10A 1B 10A

  $ hg commit -Am adda

  adding a

This is a cleaner patch generated via diff

In this case it reproduces the problem when

the output of hg export does not

import patch

  $ hg import -v -m 'b' -d '2 0' - <<EOF

  > --- a/a	2009-12-08 19:26:17.000000000 -0800

  > +++ b/a	2009-12-08 19:26:17.000000000 -0800

  > @@ -9,7 +9,7 @@

  >  A

  >  A

  >  B

  > -A

  > +a

  >  A

  >  A

  >  A

  > @@ -53,7 +53,7 @@

  >  A

  >  A

  >  B

  > -A

  > +a

  >  A

  >  A

  >  A

  > @@ -75,7 +75,7 @@

  >  A

  >  A

  >  B

  > -A

  > +a

  >  A

  >  A

  >  A

  > EOF

  applying patch from stdin

  patching file a

  Hunk #1 succeeded at 43 (offset 34 lines).

  Hunk #2 succeeded at 87 (offset 34 lines).

  Hunk #3 succeeded at 109 (offset 34 lines).

  a

compare imported changes against reference file

  $ python ../writepatterns.py aref 34X 10A 1B 1a 9A 1C 10A 1B 10A 1D 10A 1B 1a 9A 1E 10A 1B 1a 9A

  $ diff aref a