+sourcefiles := $(filter-out $(sourceincludes),$(shell $(FIND) $(FINDOPTS) $(foreach dir,$(SRCDIR),$(call quote,$(dir))) -type f '(' $(FINDRULES) ')'))
+
+ifdef GIT
+ifneq ($(wildcard $(THISDIR)/.git),)
+# (overridable) The name of the current revision of ⛩️📰 书社, or its
+# hash if the current revision is not a tag.
+thisrev = $(shell cd $(THISDIR); $(GIT) describe 2> /dev/null || $(GIT) rev-parse HEAD)
+endif
+
+ifneq ($(wildcard .git),)
+# (overridable) The name of the current revision of the working
+# directory, or its hash if the current revision is not a tag.
+srcrev = $(shell $(GIT) describe 2> /dev/null || $(GIT) rev-parse HEAD)
+endif
+endif