What's the problem of index.html in dist_web_DATA section?

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Ubuntu

web

Hi In an already existing Makefile.am, I just added index.html in dist_web_DATA section. There're several files in this section. I also added some .js files.
There're two methods of installing the application on the server:
1. sudo make install
2. building a package and installing it on the destination machine
First method causes the file to be copied to /var/www, but when I build the package and install it on the target machine, all files including old ones and what I added to this section are copied unless index.html! I changed its name to test.html and it got copied! It seems that there's a problem with the name index.html.
I may include the whole Makefile.am, but I think there's no need, because the problem is clear: There's a problem with index.html in dist_web_DATA section of Makefile.am. What's that and how can I resolve it?
Thanks

Update:

The Makefile.am is something like:

AUTOMAKE_OPTIONS = gnu

# This should be set to your web directory
webdir = @WEB_PREFIX@
# And these to the user and group of your webserver
webuser = @WEB_USER@
webgroup = @WEB_GROUP@

SUBDIRS = \
	ajax \
	css \
	graphics \
	includes \
	js \
	lang \
	skins \
	tools \
	views

dist_web_DATA = \
	index.php

# Yes, you are correct. This is a HACK!
install-data-hook:
	( cd $(DESTDIR)$(webdir); chown $(webuser):$(webgroup) $(dist_web_DATA) )
	( cd $(DESTDIR)$(webdir); chown -R $(webuser):$(webgroup) $(SUBDIRS) )
	@-( cd $(DESTDIR)$(webdir); if ! test -e events; then mkdir events; fi; chown $(webuser):$(webgroup) events; chmod u+w events )
	@-( cd $(DESTDIR)$(webdir); if ! test -e images; then mkdir images; fi; chown $(webuser):$(webgroup) images; chmod u+w images )
	@-( cd $(DESTDIR)$(webdir); if ! test -e sounds; then mkdir sounds; fi; chown $(webuser):$(webgroup) sounds; chmod u+w sounds )
	@-( cd $(DESTDIR)$(webdir); if ! test -e tools; then mkdir tools; fi; chown $(webuser):$(webgroup) tools; chmod u+w tools )
	@-( cd $(DESTDIR)$(webdir); if ! test -e temp; then mkdir temp; fi; chown $(webuser):$(webgroup) temp; chmod u+w temp )

uninstall-hook:
	@-( cd $(DESTDIR)$(webdir); rm -rf $(SUBDIRS) )
	@-( cd $(DESTDIR)$(webdir); rm -rf events images sounds tools temp )

It's indeed derived from ZoneMinder and going to customize it.

What I have tried:

I copied index.html to test.html and added it as well to Makefile.am, and I see that it's installed in /var/www unlike index.html.