mergechanges merges two or more .changes files, merging
the Architecture, Description and Files (and Checksums-*, if present)
fields of the two. There are checks made to ensure that the changes
files are from the same source package and version and use the same
changes file Format. The first changes file is used as the basis and
the information from the later ones is merged into it.
The output is normally written to stdout. If the -f
option is given, the output is written to
package_version_multi.changes instead, in the same
directory as the first changes file listed.