From 68a0d7897fa2bdf07b8ea39b67061282a4c75c7f Mon Sep 17 00:00:00 2001
From: Giovanni Campagna <gcampagna@src.gnome.org>
Date: Sat, 1 Jan 2011 16:20:34 +0100
Subject: [PATCH] Build: stop updating timestamp of st.h when not needed

Use the same approach as other generated headers (a temporary file,
compare to the existing, then copy), to avoid touching st.h, so
that other dependent objects are not rebuilt, if not needed.
It should speed up building when switching git branches, as often
config.status or automake are run, causing Makefiles to be recreated.

https://bugzilla.gnome.org/show_bug.cgi?id=638453
---
 .gitignore         | 2 ++
 src/Makefile-st.am | 9 +++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index 5a035eb4c..c3669d44c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -52,6 +52,8 @@ src/test-recorder
 src/test-recorder.ogg
 src/test-theme
 src/st.h
+src/stamp-st.h
+src/stamp-st.h.tmp
 stamp-h1
 tests/run-test.sh
 xmldocs.make
diff --git a/src/Makefile-st.am b/src/Makefile-st.am
index 4d5d5476e..579223526 100644
--- a/src/Makefile-st.am
+++ b/src/Makefile-st.am
@@ -100,11 +100,16 @@ st_source_h =					\
 	st/st-widget.h				\
 	$(NULL)
 
-st.h: Makefile
+st.h: stamp-st.h
+	@true
+stamp-st.h: Makefile
 	$(AM_V_GEN) (echo "#define ST_H_INSIDE 1";	\
 	for name in $(st_source_h); do			\
 	  echo "#include <"$$name">";			\
-	done; echo "#undef ST_H_INSIDE") > st.h.tmp && mv st.h.tmp st.h
+	done; echo "#undef ST_H_INSIDE") > $@.tmp &&  \
+	(cmp -s $@.tmp st.h || cp $@.tmp st.h) &&	\
+	rm -f $@.tmp &&				\
+	echo timestamp > $(@F)
 
 BUILT_SOURCES += st.h