Bogus svn:mergeinfo changes

[Joshua Root]

Every time a change is merged to a release branch from trunk, a handful
of files have their svn:mergeinfo property modified whether they are
affected by the change or not. The affected files are:

base/portmgr/fedora/macports.spec
base/src/pextlib1.0/sha2.c
base/src/pextlib1.0/sha2.h
base/src/pextlib1.0/sha256cmd.c
base/src/pextlib1.0/sha256cmd.h
base/src/registry2.0/receipt_sqlite.tcl

See <https://trac.macports.org/changeset/80189> for example. As you can
see, Trac says "(with no actual effect on merging)".

Does anyone know how to stop this from happening? It's not causing any
actual functional problems, but it does add irrelevant lines to the
commit logs, which makes them a little harder to read.

- Josh