Makefile: Make docs makefile portable

This patch makes the docs makefile portable with GNU Make, BSD make and
Solaris make by:
 - removing all pattern rules
 - removing all conditionals from makefile (ok in shell)
 - removing all obscure macro functions

doc/Makefile

@@ -1,25 +1,30 @@
  # Manual
 
+# IMPORTANT!
+#
+# This file is portable and compatible with GNU Make, BSD make and
+# Solaris (d)make. Do not make any changes in this file unless you
+# are certain that the changes do not break this portability.
+
+
+# a shorthand just for brevity
+m = unison-manual
+
 .PHONY: all
-all: unison-manual.pdf unison-manual.html unison-manual.txt ../src/strings.ml
+all: $(m).pdf $(m).html $(m).txt ../src/strings.ml
 
 DRAFT = false
 
--include ../src/Makefile.ProjectInfo
+include ../src/Makefile.ProjectInfo
 
 SOURCES = unison-manual.tex \
           local.tex short.tex \
           unisonversion.tex prefs.tmp prefsdocs.tmp
-FORMATS = html pdf txt dvi ps info
-FORMATS_AUX = dtxt aux htoc toc
 
-$(addprefix unison-manual., $(FORMATS) $(FORMATS_AUX)): $(SOURCES)
+$(m).pdf $(m).html $(m).txt $(m).ps: $(SOURCES)
+$(m).dtxt $(m).aux $(m).htoc $(m).toc: $(SOURCES)
 
-unison-manual-directives.tex unison-manual-text-directives.tex:
-
-ifneq ($(strip $(shell hevea -version)),)
-  HEVEA=true
-endif
+HEVEA_FOUND = test -n "$$(command -v hevea > /dev/null 2>&1 && echo true)"
 
 unisonversion.tex: ../src/Makefile.ProjectInfo
 	echo '\def\unisonversion{$(VERSION)}' > $@
@@ -28,54 +33,73 @@ unisonversion.tex: ../src/Makefile.ProjectInfo
 # jobname (or, output name for hevea) so that files for non-text versions are
 # not overwritten. Here, suffix -text is used.
 
-%-text-directives.tex:
+$(m)-text-directives.tex:
 	printf '$(TEXDIRECTIVES)\\textversiontrue\\draft$(DRAFT)' > $@
 
-%.dtxt: %.tex %-text-directives.tex
-ifeq ($(HEVEA),true)
-	hevea -o $*-text.html $<
-	(TERM=vt100; export TERM; lynx -display_charset=utf8 -dump $*-text.html > $@)
-endif
+.SUFFIXES:
+.SUFFIXES: .tex .pdf .ps .html .dtxt .txt
+
+$(m).dtxt: $(m)-text-directives.tex
 
-%.txt: %.dtxt
-ifeq ($(HEVEA),true)
-	sed -e "/^----SNIP----/,+2 d" -e "/^Junk/,$$ d" $< > $@
-endif
+.tex.dtxt:
+	if $(HEVEA_FOUND) ; then \
+	  hevea -o $*-text.html $< ; \
+	  (TERM=vt100; export TERM; lynx -display_charset=utf8 -dump $*-text.html > $@) \
+	; fi
 
-../src/strings.ml: unison-manual.dtxt docs.ml
-ifeq ($(HEVEA),true)
-	ocaml docs.ml < $< > $@
-endif
+.dtxt.txt:
+	if $(HEVEA_FOUND) ; then \
+	  sed -e "/^----SNIP----/,+2 d" -e "/^Junk/,$$ d" $< > $@ \
+	; fi
 
-%-directives.tex:
+../src/strings.ml: $(m).dtxt docs.ml
+	if $(HEVEA_FOUND) ; then \
+	  ocaml docs.ml < $(m).dtxt > $@ \
+	; fi
+
+$(m)-directives.tex:
 	printf '$(TEXDIRECTIVES)\\textversionfalse\\draft$(DRAFT)' > $@
 
 # (pdf)latex must be run multiple times to generate toc and correct references
 
-%.aux %.htoc: %.tex %-directives.tex
-	pdflatex -draftmode $<
-	pdflatex -draftmode $<
-
-%.pdf: %.tex %-directives.tex %.aux
+$(m).aux $(m).htoc &: $(m).tex $(m)-directives.tex
+	pdflatex -draftmode $(m).tex && \
+	pdflatex -draftmode $(m).tex
+# &: is the GNU Make group target separator. Other make implementations do not
+# support it but accept it nevertheless because it's treated as a target named &
+# Without group targets, the same outcome is achieved by the following:
+.ORDER: $(m).aux $(m).htoc                     # BSD make
+.NO_PARALLEL$(.MAKE.PID): $(m).aux $(m).htoc   # Solaris make
+    # BSD make interprets .NO_PARALLEL as the entire makefile not parallel.
+    # .MAKE.PID (which is only defined by BSD make) is in there just to prevent
+    # BSD make from interpreting this rule
+
+$(m).pdf: $(m).tex $(m)-directives.tex $(m).aux
+
+.tex.pdf:
 	pdflatex $<
 
-%.ps: %.pdf
+.pdf.ps:
 	pdf2ps $<
 
-%.html: %.tex %-directives.tex %.htoc
-ifeq ($(HEVEA),true)
-	hevea $<
-endif
+$(m).html: $(m).tex $(m)-directives.tex $(m).htoc
+
+.tex.html:
+	if $(HEVEA_FOUND) ; then \
+	  hevea $< \
+	; fi
 
 # Listing of preferences
-prefs.tmp: ../src/$(NAME)$(EXEC_EXT)
-	-../src/$(NAME)$(EXEC_EXT) -help > prefs.tmp
-prefsdocs.tmp: ../src/$(NAME)$(EXEC_EXT)
-	-../src/$(NAME)$(EXEC_EXT) -prefsdocs 2> prefsdocs.tmp
+prefs.tmp: ../src/$(NAME)
+	-../src/$(NAME) -help > prefs.tmp
+prefsdocs.tmp: ../src/$(NAME)
+	../src/$(NAME) -prefsdocs 2> prefsdocs.tmp
 
-../src/$(NAME)$(EXEC_EXT):
+../src/$(NAME):
 	$(MAKE) -C ../src tui
 
+RM = rm -f
+
 .PHONY: clean
 clean:
 	$(RM) -r \