Makefile: update scripts when build-time parameters change

Currently, running:

  make SHELL_PATH=/bin/bash &&
  make SHELL_PATH=/bin/sh

will not rebuild any shell scripts in the second command,
leading to incorrect results when building from an unclean
working directory.

This patch introduces a new dependency meta-file to notice
the change.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.gitignore

@@ -3,6 +3,7 @@
 /GIT-LDFLAGS
 /GIT-GUI-VARS
 /GIT-PREFIX
+/GIT-SCRIPT-DEFINES
 /GIT-USER-AGENT
 /GIT-VERSION-FILE
 /bin-wrappers/

Makefile

@@ -2007,6 +2007,8 @@ common-cmds.h: ./generate-cmdlist.sh command-list.txt
 common-cmds.h: $(wildcard Documentation/git-*.txt)
 	$(QUIET_GEN)./generate-cmdlist.sh > $@+ && mv $@+ $@
 
+SCRIPT_DEFINES = $(SHELL_PATH_SQ):$(DIFF_SQ):$(GIT_VERSION):\
+	$(localedir_SQ):$(NO_CURL):$(USE_GETTEXT_SCHEME):$(SANE_TOOL_PATH_SQ)
 define cmd_munge_script
 $(RM) $@ $@+ && \
 sed -e '1s|#!.*/sh|#!$(SHELL_PATH_SQ)|' \
@@ -2019,12 +2021,20 @@ sed -e '1s|#!.*/sh|#!$(SHELL_PATH_SQ)|' \
     $@.sh >$@+
 endef
 
-$(patsubst %.sh,%,$(SCRIPT_SH)) : % : %.sh
+GIT-SCRIPT-DEFINES: FORCE
+	@FLAGS='$(SCRIPT_DEFINES)'; \
+	    if test x"$$FLAGS" != x"`cat $@ 2>/dev/null`" ; then \
+		echo 1>&2 "    * new script parameters"; \
+		echo "$$FLAGS" >$@; \
+            fi
+
+
+$(patsubst %.sh,%,$(SCRIPT_SH)) : % : %.sh GIT-SCRIPT-DEFINES
 	$(QUIET_GEN)$(cmd_munge_script) && \
 	chmod +x $@+ && \
 	mv $@+ $@
 
-$(SCRIPT_LIB) : % : %.sh
+$(SCRIPT_LIB) : % : %.sh GIT-SCRIPT-DEFINES
 	$(QUIET_GEN)$(cmd_munge_script) && \
 	mv $@+ $@
 
@@ -2726,7 +2736,7 @@ ifndef NO_TCLTK
 	$(MAKE) -C git-gui clean
 endif
 	$(RM) GIT-VERSION-FILE GIT-CFLAGS GIT-LDFLAGS GIT-GUI-VARS GIT-BUILD-OPTIONS
-	$(RM) GIT-USER-AGENT GIT-PREFIX
+	$(RM) GIT-USER-AGENT GIT-PREFIX GIT-SCRIPT-DEFINES
 
 .PHONY: all install profile-clean clean strip
 .PHONY: shell_compatibility_test please_set_SHELL_PATH_to_a_more_modern_shell