docs: configure/Makefile changes to require at least Doxygen 1.5

Makefile.in

@@ -76,6 +76,11 @@ LDFLAGS_MIMEDB = ${LDFLAGS} @LIBS_MIMEDB@
 
 HAVE_GETTEXT=@HAVE_GETTEXT@
 
+#
+# Set to 1 if we have doxygen
+#
+
+HAVE_DOXYGEN=@HAVE_DOXYGEN@
 
 #
 #Additional .cpp files used by common.o. These also have a corresponding
@@ -258,12 +263,21 @@ MANUALS := $(addsuffix .1, $(addprefix share/man/man1/,	\
 TRANSLATIONS_SRC := $(wildcard po/*.po)
 TRANSLATIONS := $(TRANSLATIONS_SRC:.po=.gmo)
 
+#
+# If Doxygen is not available, don't attempt to build the documentation
+#
+
+ifeq ($(HAVE_DOXYGEN), 1)
+  user_doc=user_doc
+else
+  user_doc=
+endif
 
 #
 # Make everything needed for installing fish
 #
 
-all: $(PROGRAMS) user_doc share/man $(TRANSLATIONS)
+all: $(PROGRAMS) $(user_doc) share/man $(TRANSLATIONS)
 	@echo fish has now been built.
 	@echo Use \'$(MAKE) install\' to install fish.
 .PHONY: all
@@ -297,10 +311,9 @@ prof: all
 
 # Depend on the sources (*.hdr.in) and manually make the
 # intermediate *.hdr and doc.h files if needed
-# Allow doxygen to fail, e.g. if it does not exist
 
 user_doc: $(HDR_FILES_SRC) Doxyfile.user user_doc.head.html $(HELP_SRC) doc.h $(HDR_FILES)
-	- (cat Doxyfile.user ; echo PROJECT_NUMBER=@PACKAGE_VERSION@) | doxygen - && touch user_doc
+	(cat Doxyfile.user ; echo PROJECT_NUMBER=@PACKAGE_VERSION@) | doxygen - && touch user_doc
 
 
 #
@@ -839,7 +852,7 @@ clean:
 	rm -f fish-@PACKAGE_VERSION@.tar
 	rm -f fish-@PACKAGE_VERSION@.tar.gz
 	rm -f fish-@PACKAGE_VERSION@.tar.bz2
-	if command -v doxygen; then \
+	if test $(HAVE_DOXYGEN) = 1; then \
 		rm -rf doc user_doc share/man; \
 	fi
 	rm -rf fish-@PACKAGE_VERSION@

configure.ac

@@ -19,6 +19,7 @@ conf_arg=$@
 
 AC_SUBST(docdir)
 AC_SUBST(HAVE_GETTEXT)
+AC_SUBST(HAVE_DOXYGEN)
 AC_SUBST(LDFLAGS_FISH)
 AC_SUBST(LIBS_FISH)
 AC_SUBST(LIBS_FISH_INDENT)
@@ -184,6 +185,47 @@ AS_IF([test x$local_gettext != xno],
    ],
 )
 
+#
+# Build/clean the documentation only if Doxygen is available
+#
+
+doxygen_minimum=1.5
+
+AC_ARG_WITH(
+  doxygen,
+  AS_HELP_STRING(
+    [--with-doxygen],
+    [use Doxygen to regenerate documentation]
+  ),
+  [use_doxygen=$withval],
+  [use_doxygen=auto]
+)
+
+AS_IF([test "$use_doxygen" != "no"],
+  [
+    AC_CHECK_PROGS([found_doxygen], [doxygen], [no])
+    if test "$found_doxygen" != no; then
+      # test version
+      AC_MSG_CHECKING([the doxygen version])
+      doxygen_version=`doxygen --version 2>/dev/null`
+      AC_MSG_RESULT([$doxygen_version])
+      AS_VERSION_COMPARE([$doxygen_version], [$doxygen_minimum],
+        [ if test "$use_doxygen" = auto; then
+            AC_MSG_WARN([doxygen version $doxygen_version found, but $doxygen_minimum required])
+            HAVE_DOXYGEN=0
+          else
+            AC_MSG_FAILURE([doxygen version $doxygen_version found, but $doxygen_minimum required])
+          fi
+        ],
+        [HAVE_DOXYGEN=1], [HAVE_DOXYGEN=1])
+    elif test "$use_doxygen" != auto; then
+      AC_MSG_FAILURE([--with-doxygen was given, but the doxygen program could not be found])
+    else
+      HAVE_DOXYGEN=0
+    fi
+  ],
+)
+
 #
 # Try to enable large file support. This will make sure that on systems
 # where off_t can be either 32 or 64 bit, the latter size is used. On