doc: configure detection of sphinx and rst2man

Because sphinx-build does not provide a convenient way of listing
which builders exist, and some people actually have pre 1.0 sphinx, we
try loading a relevant python module.

Currently the assumption is that no python in path -> no sphinx-build
in path.

configure

@@ -393,6 +393,25 @@ else
     have_emacs=0
 fi
 
+printf "Checking if sphinx is available and supports nroff output... "
+if hash sphinx-build > /dev/null 2>&1 && python -m sphinx.writers.manpage > /dev/null 2>&1 ; then
+    printf "Yes.\n"
+    have_sphinx=1
+    have_rst2man=0
+else
+    printf "No (falling back to rst2man).\n"
+    have_sphinx=0
+
+    printf "Checking if rst2man is available... "
+    if rst2man -V > /dev/null 2>&1; then
+       printf "Yes.\n"
+       have_rst2man=1
+    else
+       printf "No (so will not install man pages).\n"
+       have_rst2man=0
+    fi
+fi
+
 libdir_in_ldconfig=0
 
 printf "Checking which platform we are on... "
@@ -759,6 +778,12 @@ emacsetcdir=${EMACSETCDIR}
 # Whether there's an emacs binary available for byte-compiling
 HAVE_EMACS = ${have_emacs}
 
+# Whether there's a sphinx-build binary available for building documentation
+HAVE_SPHINX=${have_sphinx}
+
+# Whether there's a rst2man binary available for building documentation
+HAVE_RST2MAN=${have_rst2man}
+
 # The directory to which desktop files should be installed
 desktop_dir = \$(prefix)/share/applications
 

doc/Makefile.local

@@ -33,11 +33,9 @@ sphinx-info: sphinx-texinfo
 
 MAN_GZIP_FILES := $(addsuffix .gz,${MAN_ROFF_FILES})
 
-build-man: ${MAN_GZIP_FILES}
+# Use the man page converter that is available. We should never depend
-
+# on MAN_ROFF_FILES if a converter is not available.
-${MAN_ROFF_FILES}: ${dir}/man.stamp
+${MAN_ROFF_FILES}: ${MAN_RST_FILES}
-
-$(dir)/man.stamp: ${MAN_RST_FILES}
 ifeq ($(HAVE_SPHINX),1)
 	$(SPHINXBUILD) -b man $(ALLSPHINXOPTS) $(DOCBUILDDIR)/man
 	for section in 1 5 7; do \
@@ -46,11 +44,19 @@ ifeq ($(HAVE_SPHINX),1)
 	done
 else ifeq ($(HAVE_RST2MAN),1)
 	$(prerst2man) $(DOCBUILDDIR)/.. $(DOCBUILDDIR)/man
-	touch $@
 else
-	@echo "No sphinx or rst2man, will not install man pages."
+	@echo "Fatal: build dependency fail."
+	@false
 endif
 
+# Do not try to build or install man pages if a man page converter is
+# not available.
+ifeq ($(HAVE_SPHINX)$(HAVE_RST2MAN),00)
+build-man:
+install-man:
+	@echo "No sphinx or rst2man, will not install man pages."
+else
+build-man: ${MAN_GZIP_FILES}
 install-man: ${MAN_GZIP_FILES}
 	mkdir -p "$(DESTDIR)$(mandir)/man1"
 	mkdir -p "$(DESTDIR)$(mandir)/man5"
@@ -59,6 +65,7 @@ install-man: ${MAN_GZIP_FILES}
 	install -m0644 $(DOCBUILDDIR)/man/man5/*.5.gz $(DESTDIR)/$(mandir)/man5
 	install -m0644 $(DOCBUILDDIR)/man/man7/*.7.gz $(DESTDIR)/$(mandir)/man7
 	cd $(DESTDIR)/$(mandir)/man1 && ln -sf notmuch.1.gz notmuch-setup.1.gz
+endif
 
 $(dir)/docdeps.mk: $(dir)/conf.py $(dir)/mkdocdeps.py
 	$(mkdocdeps) $< $(DOCBUILDDIR) $@