$ cat > writepatterns.py < 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' - < --- 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). committing files: a committing manifest committing changelog created 189885cecb41 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 $ cd ..