The swapped patches are sent to standard output, with a marker line ("=== 8< === cut here === 8< ===") between them, unless the --in-place option is passed. In that case, the output is written back to the original input files.
-p n, --strip-match=n
-U n, --unified=n
-d pattern, --drop-context=PATTERN
Note that the interpretation of the shell wildcard pattern does not count slash characters or periods as special (in other words, no flags are given to fnmatch). This is so that "*/basename"-type patterns can be given without limiting the number of pathname components.
This is only been very lightly tested, and may not even work. Using --in-place is not recommended at the moment.
There are some cases in which it is not possible to meaningfully flip patches without understanding the semantics of the content. This program only uses complete lines that appear at some stage during the application of the two patches, and never composes a line from parts.
Tim Waugh <email@example.com>