Why creating local dirs when disting?

[Akim Demaille]

I don't understand this:

~/src/am % make -s check TESTS=distdir.test                      nostromo Err 2
Making check in .
Making check in m4
Making check in tests
PASS: distdir.test
==================
All 1 tests passed
==================
~/src/am % grep -C10 'mkinstall.*foo' tests/testSubDir/Makefile.in
DISTFILES = $(DIST_COMMON) $(DIST_SOURCES) $(TEXINFOS) $(EXTRA_DIST)

top_distdir = .
distdir = $(top_distdir)/$(PACKAGE)-$(VERSION)

GZIP_ENV = --best

distdir: $(DISTFILES)
        -chmod -R a+w $(distdir) >/dev/null 2>&1; rm -rf $(distdir)
        mkdir $(distdir)
        $(mkinstalldirs) $(distdir)/foo foo <<<<<<<<<<<<<<<========
        @for file in $(DISTFILES); do \
          d=$(srcdir); \
          if test -d $$d/$$file; then \
            cp -pR $$d/$$file $(distdir) \
            || exit 1; \
          else \
            test -f $(distdir)/$$file \
            || cp -p $$d/$$file $(distdir)/$$file \
            || exit 1; \
          fi; \
~/src/am % cat tests/testSubDir/Makefile.am                      nostromo 10:36
EXTRA_DIST = foo/bar ./joe

What is this second foo doing here?