libpq.rc make rule

The libpq.rc make rule says:

# depend on Makefile.global to force rebuild on re-run of configure
$(srcdir)/libpq.rc: libpq.rc.in $(top_builddir)/src/Makefile.global
sed -e 's/\(VERSION.*\),0 *$$/\1,'`date '+%y%j' | sed 's/^0*//'`'/' < $< > $@

However, libpq.rc is also included in the distribution, so whenever a
distribution is built, the distributed file would be overwritten, which is
not a nice thing to do.

Could someone explain what the requirement behind this is? The '+%y%j'
changes every day. Why is libpq the only subsystem that needs a daily
version number?

--
Peter Eisentraut
http://developer.postgresql.org/~petere/