Merge branch 'ab/sha1dc-build'

Push the submodule version of collision-detecting SHA-1 hash
implementation a bit harder on builders.

* ab/sha1dc-build:
  sha1dc_git.h: re-arrange an ifdef chain for a subsequent change
  Makefile: under "make dist", include the sha1collisiondetection submodule
  Makefile: don't error out under DC_SHA1_EXTERNAL if DC_SHA1_SUBMODULE=auto

Author: gitster

Makefile

@@ -1513,7 +1513,9 @@ else
 	LIB_OBJS += sha1dc_git.o
 ifdef DC_SHA1_EXTERNAL
 	ifdef DC_SHA1_SUBMODULE
+		ifneq ($(DC_SHA1_SUBMODULE),auto)
 $(error Only set DC_SHA1_EXTERNAL or DC_SHA1_SUBMODULE, not both)
+		endif
 	endif
 	BASIC_CFLAGS += -DDC_SHA1_EXTERNAL
 	EXTLIBS += -lsha1detectcoll
@@ -2668,6 +2670,21 @@ dist: git-archive$(X) configure
 		$(GIT_TARNAME)/configure \
 		$(GIT_TARNAME)/version \
 		$(GIT_TARNAME)/git-gui/version
+ifdef DC_SHA1_SUBMODULE
+	@mkdir -p $(GIT_TARNAME)/sha1collisiondetection/lib
+	@cp sha1collisiondetection/LICENSE.txt \
+		$(GIT_TARNAME)/sha1collisiondetection/
+	@cp sha1collisiondetection/LICENSE.txt \
+		$(GIT_TARNAME)/sha1collisiondetection/
+	@cp sha1collisiondetection/lib/sha1.[ch] \
+		$(GIT_TARNAME)/sha1collisiondetection/lib/
+	@cp sha1collisiondetection/lib/ubc_check.[ch] \
+		$(GIT_TARNAME)/sha1collisiondetection/lib/
+	$(TAR) rf $(GIT_TARNAME).tar \
+		$(GIT_TARNAME)/sha1collisiondetection/LICENSE.txt \
+		$(GIT_TARNAME)/sha1collisiondetection/lib/sha1.[ch] \
+		$(GIT_TARNAME)/sha1collisiondetection/lib/ubc_check.[ch]
+endif
 	@$(RM) -r $(GIT_TARNAME)
 	gzip -f -9 $(GIT_TARNAME).tar
 

sha1dc_git.h

@@ -1,9 +1,9 @@
 /* Plumbing with collition-detecting SHA1 code */
 
-#ifdef DC_SHA1_SUBMODULE
-#include "sha1collisiondetection/lib/sha1.h"
-#elif defined(DC_SHA1_EXTERNAL)
+#ifdef DC_SHA1_EXTERNAL
 #include <sha1dc/sha1.h>
+#elif defined(DC_SHA1_SUBMODULE)
+#include "sha1collisiondetection/lib/sha1.h"
 #else
 #include "sha1dc/sha1.h"
 #endif