version: Print git id if present

If criu is built from git repo print git commit id, convenient for debug.

For example

 | $ ./criu -V
 | Version: 0.7
 | GitID: 7985251
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

crtools.c

@@ -266,6 +266,8 @@ int main(int argc, char *argv[])
 			break;
 		case 'V':
 			pr_msg("Version: %s\n", CRIU_VERSION);
+			if (strcmp(CRIU_GITID, "0"))
+				pr_msg("GitID: %s\n", CRIU_GITID);
 			return 0;
 		case 'h':
 		default:

scripts/Makefile.version

 CRTOOLSVERSION		:= $(VERSION_MAJOR)$(if $(VERSION_MINOR),.$(VERSION_MINOR))$(if $(VERSION_SUBLEVEL),.$(VERSION_SUBLEVEL))
 
 VERSION_HEADER := include/version.h
+GITID := $(shell if [ -d ".git" ]; then git reflog -n 1 | cut -f1 -d' '; fi)
+ifeq ($(GITID),)
+	GITID := 0
+endif
 
 $(VERSION_HEADER): Makefile scripts/Makefile.version
 	$(E) "  GEN     " $@
@@ -10,6 +14,7 @@ $(VERSION_HEADER): Makefile scripts/Makefile.version
 	$(Q) echo "#define CRIU_VERSION \"$(CRTOOLSVERSION)\""		>> $(VERSION_HEADER)
 	$(Q) echo "#define CRIU_VERSION_MAJOR " $(VERSION_MAJOR)	>> $(VERSION_HEADER)
 	$(Q) echo "#define CRIU_VERSION_MINOR " $(VERSION_MINOR)	>> $(VERSION_HEADER)
+	$(Q) echo "#define CRIU_GITID \"$(GITID)\""			>> $(VERSION_HEADER)
 	$(Q) echo "#endif /* __CR_VERSION_H__ */"			>> $(VERSION_HEADER)
 
 ##