[PATCH 3/5] tools lib subcmd: Add dependency test to install_headers

[Ian Rogers]

Compute the headers to be installed from their source headers and make
each have its own build target to install it. Using dependencies
avoids headers being reinstalled and getting a new timestamp which
then causes files that depend on the header to be rebuilt.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/lib/subcmd/Makefile | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/tools/lib/subcmd/Makefile b/tools/lib/subcmd/Makefile
index 9a316d8b89df..b87213263a5e 100644
--- a/tools/lib/subcmd/Makefile
+++ b/tools/lib/subcmd/Makefile
@@ -89,10 +89,10 @@ define do_install_mkdir
 endef
 
 define do_install
-	if [ ! -d '$(DESTDIR_SQ)$2' ]; then             \
-		$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$2'; \
+	if [ ! -d '$2' ]; then             \
+		$(INSTALL) -d -m 755 '$2'; \
 	fi;                                             \
-	$(INSTALL) $1 $(if $3,-m $3,) '$(DESTDIR_SQ)$2'
+	$(INSTALL) $1 $(if $3,-m $3,) '$2'
 endef
 
 install_lib: $(LIBFILE)
@@ -100,13 +100,16 @@ install_lib: $(LIBFILE)
 		$(call do_install_mkdir,$(libdir_SQ)); \
 		cp -fpR $(LIBFILE) $(DESTDIR)$(libdir_SQ)
 
-install_headers:
-	$(call QUIET_INSTALL, libsubcmd_headers) \
-		$(call do_install,exec-cmd.h,$(prefix)/include/subcmd,644); \
-		$(call do_install,help.h,$(prefix)/include/subcmd,644); \
-		$(call do_install,pager.h,$(prefix)/include/subcmd,644); \
-		$(call do_install,parse-options.h,$(prefix)/include/subcmd,644); \
-		$(call do_install,run-command.h,$(prefix)/include/subcmd,644);
+HDRS := exec-cmd.h help.h pager.h parse-options.h run-command.h
+INSTALL_HDRS_PFX := $(DESTDIR)$(prefix)/include/subcmd
+INSTALL_HDRS := $(addprefix $(INSTALL_HDRS_PFX)/, $(HDRS))
+
+$(INSTALL_HDRS): $(INSTALL_HDRS_PFX)/%.h: %.h
+	$(call QUIET_INSTALL, $@) \
+		$(call do_install,$<,$(INSTALL_HDRS_PFX)/,644)
+
+install_headers: $(INSTALL_HDRS)
+	$(call QUIET_INSTALL, libsubcmd_headers)
 
 install: install_lib install_headers
 
-- 
2.39.0.rc0.267.gcb52ba06e7-goog