Merge branch 'jn/less-reconfigure'

A change made on v1.8.1.x maintenance track had a nasty regression
to break the build when autoconf is used.

* jn/less-reconfigure:
  Makefile: avoid infinite loop on configure.ac change

Author: gitster

Makefile

@@ -1821,12 +1821,14 @@ $(patsubst %.py,%,$(SCRIPT_PYTHON)): % : unimplemented.sh
 	mv $@+ $@
 endif # NO_PYTHON
 
+CONFIGURE_RECIPE = $(RM) configure configure.ac+ && \
+		   sed -e 's/@@GIT_VERSION@@/$(GIT_VERSION)/g' \
+			configure.ac >configure.ac+ && \
+		   autoconf -o configure configure.ac+ && \
+		   $(RM) configure.ac+
+
 configure: configure.ac GIT-VERSION-FILE
-	$(QUIET_GEN)$(RM) $@ $<+ && \
-	sed -e 's/@@GIT_VERSION@@/$(GIT_VERSION)/g' \
-	    $< > $<+ && \
-	autoconf -o $@ $<+ && \
-	$(RM) $<+
+	$(QUIET_GEN)$(CONFIGURE_RECIPE)
 
 ifdef AUTOCONFIGURED
 # We avoid depending on 'configure' here, because it gets rebuilt
@@ -1835,7 +1837,7 @@ ifdef AUTOCONFIGURED
 # do want to recheck when the platform/environment detection logic
 # changes, hence this depends on configure.ac.
 config.status: configure.ac
-	$(QUIET_GEN)$(MAKE) configure && \
+	$(QUIET_GEN)$(CONFIGURE_RECIPE) && \
 	if test -f config.status; then \
 	  ./config.status --recheck; \
 	else \