Makefile: propagate Git version via generated header

We set up a couple of preprocessor macros when compiling Git that
propagate the version that Git was built from to `git version` et al.
The way this is set up makes it harder than necessary to reuse the
infrastructure across the different build systems.

Refactor this such that we generate a "version-def.h" header via
`GIT-VERSION-GEN` instead.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.gitignore

@@ -195,6 +195,7 @@
 /config-list.h
 /command-list.h
 /hook-list.h
+/version-def.h
 *.tar.gz
 *.dsc
 *.deb

GIT-VERSION-GEN

@@ -52,6 +52,11 @@ else
 fi
 
 GIT_VERSION=$(expr "$VN" : v*'\(.*\)')
+GIT_BUILT_FROM_COMMIT=$(git -C "$SOURCE_DIR" rev-parse -q --verify HEAD 2>/dev/null)
+if test -z "$GIT_USER_AGENT"
+then
+	GIT_USER_AGENT="git/$GIT_VERSION"
+fi
 
 read GIT_MAJOR_VERSION GIT_MINOR_VERSION GIT_MICRO_VERSION trailing <<EOF
 $(echo "$GIT_VERSION" 0 0 0 | tr '.a-zA-Z-' ' ')
@@ -61,6 +66,8 @@ sed -e "s|@GIT_VERSION@|$GIT_VERSION|" \
 	-e "s|@GIT_MAJOR_VERSION@|$GIT_MAJOR_VERSION|" \
 	-e "s|@GIT_MINOR_VERSION@|$GIT_MINOR_VERSION|" \
 	-e "s|@GIT_MICRO_VERSION@|$GIT_MICRO_VERSION|" \
+	-e "s|@GIT_BUILT_FROM_COMMIT@|$GIT_BUILT_FROM_COMMIT|" \
+	-e "s|@GIT_USER_AGENT@|$GIT_USER_AGENT|" \
 	"$INPUT" >"$OUTPUT"+
 
 if ! test -f "$OUTPUT" || ! cmp "$OUTPUT"+ "$OUTPUT" >/dev/null

Makefile

@@ -2508,13 +2508,11 @@ PAGER_ENV_CQ_SQ = $(subst ','\'',$(PAGER_ENV_CQ))
 pager.sp pager.s pager.o: EXTRA_CPPFLAGS = \
 	-DPAGER_ENV='$(PAGER_ENV_CQ_SQ)'
 
-version.sp version.s version.o: GIT-VERSION-FILE GIT-USER-AGENT
-version.sp version.s version.o: EXTRA_CPPFLAGS = \
-	'-DGIT_VERSION="$(GIT_VERSION)"' \
-	'-DGIT_USER_AGENT=$(GIT_USER_AGENT_CQ_SQ)' \
-	'-DGIT_BUILT_FROM_COMMIT="$(shell \
-		GIT_CEILING_DIRECTORIES="$(CURDIR)/.." \
-		git rev-parse -q --verify HEAD 2>/dev/null)"'
+version-def.h: version-def.h.in GIT-VERSION-GEN GIT-VERSION-FILE GIT-USER-AGENT
+	$(QUIET_GEN)GIT_USER_AGENT="$(GIT_USER_AGENT)" $(SHELL_PATH) ./GIT-VERSION-GEN "$(shell pwd)" $< $@+
+	@if cmp $@+ $@ >/dev/null 2>&1; then $(RM) $@+; else mv $@+ $@; fi
+
+version.sp version.s version.o: version-def.h
 
 $(BUILT_INS): git$X
 	$(QUIET_BUILT_IN)$(RM) $@ && \
@@ -3728,6 +3726,7 @@ clean: profile-clean coverage-clean cocciclean
 	$(RM) $(FUZZ_PROGRAMS)
 	$(RM) $(SP_OBJ)
 	$(RM) $(HCC)
+	$(RM) version-def.h
 	$(RM) -r bin-wrappers $(dep_dirs) $(compdb_dir) compile_commands.json
 	$(RM) -r po/build/
 	$(RM) *.pyc *.pyo */*.pyc */*.pyo $(GENERATED_H) $(ETAGS_TARGET) tags cscope*

contrib/buildsystems/CMakeLists.txt

@@ -229,10 +229,7 @@ add_compile_definitions(PAGER_ENV="LESS=FRX LV=-c"
 			GIT_HTML_PATH="share/doc/git-doc"
 			DEFAULT_HELP_FORMAT="html"
 			DEFAULT_GIT_TEMPLATE_DIR="share/git-core/templates"
-			GIT_VERSION="${PROJECT_VERSION}.GIT"
-			GIT_USER_AGENT="git/${PROJECT_VERSION}.GIT"
-			BINDIR="bin"
-			GIT_BUILT_FROM_COMMIT="")
+			BINDIR="bin")
 
 if(WIN32)
 	set(FALLBACK_RUNTIME_PREFIX /mingw64)
@@ -668,6 +665,17 @@ parse_makefile_for_sources(libgit_SOURCES "LIB_OBJS")
 
 list(TRANSFORM libgit_SOURCES PREPEND "${CMAKE_SOURCE_DIR}/")
 list(TRANSFORM compat_SOURCES PREPEND "${CMAKE_SOURCE_DIR}/")
+
+add_custom_command(OUTPUT "${CMAKE_BINARY_DIR}/version-def.h"
+	COMMAND "${SH_EXE}" "${CMAKE_SOURCE_DIR}/GIT-VERSION-GEN"
+		"${CMAKE_SOURCE_DIR}"
+		"${CMAKE_SOURCE_DIR}/version-def.h.in"
+		"${CMAKE_BINARY_DIR}/version-def.h"
+	DEPENDS "${SH_EXE}" "${CMAKE_SOURCE_DIR}/GIT-VERSION-GEN"
+		"${CMAKE_SOURCE_DIR}/version-def.h.in"
+	VERBATIM)
+list(APPEND libgit_SOURCES "${CMAKE_BINARY_DIR}/version-def.h")
+
 add_library(libgit ${libgit_SOURCES} ${compat_SOURCES})
 
 #libxdiff

version-def.h.in

@@ -0,0 +1,8 @@
+#ifndef VERSION_DEF_H
+#define VERSION_DEF_H
+
+#define GIT_VERSION "@GIT_VERSION@"
+#define GIT_BUILT_FROM_COMMIT "@GIT_BUILT_FROM_COMMIT@"
+#define GIT_USER_AGENT "@GIT_USER_AGENT@"
+
+#endif /* VERSION_DEF_H */

version.c

@@ -1,5 +1,6 @@
 #include "git-compat-util.h"
 #include "version.h"
+#include "version-def.h"
 #include "strbuf.h"
 
 const char git_version_string[] = GIT_VERSION;