[PATCH v4 10/23] Makefile: create a GIT-PYTHON-DEFINES, like "PERL"

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Create a new "GIT-PYTHON-DEFINES" file, and untangle the dependency
issues of the Python by copying over the patterns established for
building the adjacent Perl code in preceding commits.

As with Perl, there's no real reason to depend on GIT-BUILD-OPTIONS or
GIT-CFLAGS when building the Python code, nor did we need
GIT-PREFIX. Let's instead add those variables we care about to a
"GIT-PYTHON-DEFINES" and depend on that.

This changes code originally added in ca3bcabf118 (auto-detect changed
prefix and/or changed build flags, 2006-06-15), and adjusted in
96a4647fca5 (Makefile: detect when PYTHON_PATH changes, 2012-12-18).

The relevant code for the "Perl" targets was then added in
07981dce81e (Makefile: rebuild perl scripts when perl paths change,
2013-11-18), and has been adjusted in preceding commits.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 .gitignore |  2 +-
 Makefile   | 49 +++++++++++++++++++++++++------------------------
 2 files changed, 26 insertions(+), 25 deletions(-)

diff --git a/.gitignore b/.gitignore
index 054249b20a8..845e5d0c355 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,7 +8,7 @@
 /GIT-PREFIX
 /GIT-PERL-DEFINES
 /GIT-PERL-HEADER
-/GIT-PYTHON-VARS
+/GIT-PYTHON-DEFINES
 /GIT-SCRIPT-DEFINES
 /GIT-USER-AGENT
 /GIT-VERSION-FILE
diff --git a/Makefile b/Makefile
index 361abff2402..c698c5b058a 100644
--- a/Makefile
+++ b/Makefile
@@ -2378,18 +2378,15 @@ GIT-PERL-DEFINES: FORCE
 		echo "$$FLAGS" >$@; \
 	    fi
 
-# This makes sure we depend on the NO_PYTHON setting itself.
-$(SCRIPT_PYTHON_GEN): GIT-BUILD-OPTIONS
+# As with NO_PERL=Y we'll still make GIT-PYTHON-DEFINES if "NO_PYTHON"
+# is defined, for creating the "unimplemented.sh" scripts.
+PYTHON_DEFINES =
+$(SCRIPT_PYTHON_GEN): GIT-PYTHON-DEFINES
+
+ifdef NO_PYTHON
+PYTHON_DEFINES += $(SHELL_PATH_SQ)
+PYTHON_DEFINES += $(NO_PYTHON)
 
-ifndef NO_PYTHON
-$(SCRIPT_PYTHON_GEN): GIT-CFLAGS GIT-PREFIX GIT-PYTHON-VARS
-$(SCRIPT_PYTHON_GEN): % : %.py
-	$(QUIET_GEN) \
-	sed -e '1s|#!.*python|#!$(PYTHON_PATH_SQ)|' \
-	    $< >$@+ && \
-	chmod +x $@+ && \
-	mv $@+ $@
-else # NO_PYTHON
 $(SCRIPT_PYTHON_GEN): % : unimplemented.sh
 	$(QUIET_GEN) \
 	sed -e '1s|#!.*/sh|#!$(SHELL_PATH_SQ)|' \
@@ -2397,8 +2394,24 @@ $(SCRIPT_PYTHON_GEN): % : unimplemented.sh
 	    unimplemented.sh >$@+ && \
 	chmod +x $@+ && \
 	mv $@+ $@
+else # NO_PYTHON
+PYTHON_DEFINES += $(PYTHON_PATH_SQ)
+
+$(SCRIPT_PYTHON_GEN): % : %.py GIT-PYTHON-DEFINES
+	$(QUIET_GEN) \
+	sed -e '1s|#!.*python|#!$(PYTHON_PATH_SQ)|' \
+	    $< >$@+ && \
+	chmod +x $@+ && \
+	mv $@+ $@
 endif # NO_PYTHON
 
+GIT-PYTHON-DEFINES: FORCE
+	@FLAGS='$(PYTHON_DEFINES)'; \
+	    if test x"$$FLAGS" != x"`cat $@ 2>/dev/null`" ; then \
+		echo >&2 "    * new python-specific parameters"; \
+		echo "$$FLAGS" >$@; \
+	    fi
+
 CONFIGURE_RECIPE = sed -e 's/@@GIT_VERSION@@/$(GIT_VERSION)/g' \
 			configure.ac >configure.ac+ && \
 		   autoconf -o configure configure.ac+ && \
@@ -2848,18 +2861,6 @@ else
 endif
 	@if cmp $@+ $@ >/dev/null 2>&1; then $(RM) $@+; else mv $@+ $@; fi
 
-### Detect Python interpreter path changes
-ifndef NO_PYTHON
-TRACK_PYTHON = $(subst ','\'',-DPYTHON_PATH='$(PYTHON_PATH_SQ)')
-
-GIT-PYTHON-VARS: FORCE
-	@VARS='$(TRACK_PYTHON)'; \
-	    if test x"$$VARS" != x"`cat $@ 2>/dev/null`" ; then \
-		echo >&2 "    * new Python interpreter location"; \
-		echo "$$VARS" >$@; \
-            fi
-endif
-
 test_bindir_programs := $(patsubst %,bin-wrappers/%,$(BINDIR_PROGRAMS_NEED_X) $(BINDIR_PROGRAMS_NO_X) $(TEST_PROGRAMS_NEED_X))
 
 all:: $(TEST_PROGRAMS) $(test_bindir_programs)
@@ -3256,7 +3257,7 @@ ifndef NO_TCLTK
 endif
 	$(RM) GIT-VERSION-FILE GIT-CFLAGS GIT-LDFLAGS GIT-BUILD-OPTIONS
 	$(RM) GIT-USER-AGENT GIT-PREFIX
-	$(RM) GIT-SCRIPT-DEFINES GIT-PERL-DEFINES GIT-PERL-HEADER GIT-PYTHON-VARS
+	$(RM) GIT-SCRIPT-DEFINES GIT-PERL-DEFINES GIT-PERL-HEADER GIT-PYTHON-DEFINES
 ifdef MSVC
 	$(RM) $(patsubst %.o,%.o.pdb,$(OBJECTS))
 	$(RM) $(patsubst %.exe,%.pdb,$(OTHER_PROGRAMS))
-- 
2.34.0.796.g2c87ed6146a