doc/Makefile: add help/*.txt as a dependency

doc/Makefile

@@ -1,46 +1,47 b''
 SOURCES=$(wildcard *.[0-9].txt)
 MAN=$(SOURCES:%.txt=%)
 HTML=$(SOURCES:%.txt=%.html)
+GENDOC=gendoc.py ../mercurial/commands.py ../mercurial/help.py ../help/*.txt
 PREFIX=/usr/local
 MANDIR=$(PREFIX)/share/man
 INSTALL=install -c -m 644
 PYTHON=python
 RST2HTML=$(shell which rst2html 2> /dev/null || which rst2html.py)
 
 all: man html
 
 man: $(MAN)
 
 html: $(HTML)
 
 hg.1.txt: hg.1.gendoc.txt
 	touch hg.1.txt
 
-hg.1.gendoc.txt: gendoc.py ../mercurial/commands.py ../mercurial/help.py
+hg.1.gendoc.txt: $(GENDOC)
 	${PYTHON} gendoc.py > $@.tmp
 	mv $@.tmp $@
 
 %: %.txt common.txt
 	$(PYTHON) rst2man.py --halt warning \
 	  --strip-elements-with-class htmlonly $*.txt $*
 
 %.html: %.txt common.txt
 	$(RST2HTML) --halt warning \
 	  --link-stylesheet --stylesheet-path style.css $*.txt $*.html
 
 MANIFEST: man html
 # tracked files are already in the main MANIFEST
 	$(RM) $@
 	for i in $(MAN) $(HTML) hg.1.gendoc.txt; do \
 	  echo "doc/$$i" >> $@ ; \
 	done
 
 install: man
 	for i in $(MAN) ; do \
 	  subdir=`echo $$i | sed -n 's/^.*\.\([0-9]\)$$/man\1/p'` ; \
 	  mkdir -p $(DESTDIR)$(MANDIR)/$$subdir ; \
 	  $(INSTALL) $$i $(DESTDIR)$(MANDIR)/$$subdir ; \
 	done
 
 clean:
 	$(RM) $(MAN) $(MAN:%=%.html) *.[0-9].gendoc.txt MANIFEST