use DESTDIR both places its needed

doc/Makefile

@@ -1,44 +1,44 b''
 SOURCES=$(wildcard *.[0-9].txt)
 MAN=$(SOURCES:%.txt=%)
 HTML=$(SOURCES:%.txt=%.html)
 PREFIX=/usr/local
 MANDIR=$(PREFIX)/share/man
 INSTALL=install -c
 
 all: man html
 
 man: $(MAN)
 
 html: $(HTML)
 
 hg.1.txt: hg.1.gendoc.txt
 	touch hg.1.txt
 
 hg.1.gendoc.txt: ../mercurial/commands.py ../mercurial/help.py
 	python gendoc.py > $@
 
 %: %.xml
 	xmlto man $*.xml
 
 %.xml: %.txt
 	asciidoc -d manpage -b docbook $*.txt
 
 %.html: %.txt
 	asciidoc -b html4 $*.txt || asciidoc -b html $*.txt
 
 MANIFEST: man html
 	# versionned 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/..*\.\([0-9]\)$$/man\1/p'` ; \
-	  mkdir -p $(MANDIR)/$$subdir ; \
+	  mkdir -p $(DESTDIR)/$(MANDIR)/$$subdir ; \
 	  $(INSTALL) $$i $(DESTDIR)/$(MANDIR)/$$subdir ; \
 	done
 
 clean:
 	$(RM) $(MAN) $(MAN:%=%.xml) $(MAN:%=%.html) *.[0-9].gendoc.txt MANIFEST