[mm-common] doc-reference.am: Don't assume all existing html files shall be rebuilt

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 1ed83c95f60bf6e10a148e43fd4e4201761d2459
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Tue Aug 11 10:13:40 2015 +0200

    doc-reference.am: Don't assume all existing html files shall be rebuilt
    
    * build/doc-reference.am: Don't use the set of previously generated files as
    prerequisites when building reference documentation. Use html/index.html as a
    prerequisite, forcing a rebuild of html/* if it's missing. Bug #686364.

 build/doc-reference.am |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/build/doc-reference.am b/build/doc-reference.am
index 975d23f..1578b2f 100644
--- a/build/doc-reference.am
+++ b/build/doc-reference.am
@@ -68,10 +68,12 @@ htmlrefdir   = $(referencedir)/html
 devhelpdir   = $(datadir)/devhelp/books/$(book_name)
 
 if ENABLE_DOCUMENTATION
+doc_build_files  = $(doc_outdir)/html/index.html $(doxytagfile) $(devhelpfile)
 doc_inst_targets = install-htmlref install-devhelp
 doc_inst_files   = $(doxytagfile)
 doc_dist_files   = $(devhelpfile) $(call vpath_listall,$(htmlref_patterns))
 else
+doc_build_files  =
 doc_inst_targets =
 doc_inst_files   =
 doc_dist_files   =
@@ -133,8 +135,11 @@ else
 doc_dependencies =
 endif
 
-# Explicitly depend on the files to be distributed or installed.
-all-local: $(doc_inst_files) $(doc_dist_files)
+# Depend on the files that we know shall be built.
+# $(call vpath_listall,$(htmlref_patterns)) is not used as a prerequisite.
+# It would expand to files that exist when the make command is issued,
+# which is not necessarily the set of files that shall be built.
+all-local: $(doc_build_files)
 
 # Hook up custom rules for translating references to external documentation
 # to the actual location at install time.
@@ -190,7 +195,7 @@ $(doc_outdir)/html/%: | $(doxytagfile)
 # Quote $(DOXYGEN) so that this still works if this is a path containing
 # spaces such as "/c/Program Files (x86)/Doxygen/bin/doxygen"
 # The doc_config file may contain "$(MMDOCTOOLDIR)". Export MMDOCTOOLDIR to Doxygen.
-$(doxytagfile): $(doc_dependencies) | $(doc_config)
+$(doc_outdir)/html/index.html $(doxytagfile): $(doc_dependencies) | $(doc_config)
        -$(AM_V_at)rm -f $@
        -$(AM_V_at)rm -fr $(doc_outdir)/html
        $(AM_V_GEN)(echo '@INCLUDE =' $(doc_config) && echo 'INPUT =' $(doc_input)) | 
MMDOCTOOLDIR="$(MMDOCTOOLDIR)" "$(DOXYGEN)" -