Node:Imperfect, Next:Creating and Removing, Previous:Revision Control, Up:Merging with patch
patch tries to skip any leading text in the patch file,
apply the diff, and then skip any trailing text.  Thus you can feed a
mail message directly to patch, and it should work.  If the
entire diff is indented by a constant amount of white space,
patch automatically ignores the indentation.  If a context
diff contains trailing carriage return on each line, patch
automatically ignores the carriage return.  If a context diff has been
encapsulated by prepending -  to lines beginning with -
as per Internet RFC 934,
patch automatically unencapsulates the input.
However, certain other types of imperfect input require user intervention or testing.
patch find close matches. 
patch will do.