Makefile: reduce the number of git operations

dmerejkowsky · dmerejkowsky · commit b595bee84f19 · 2021-05-04T14:31:43.000+02:00
Running `git checkout CPYTHON_CURRENT_COMMIT` and then
`git checkout -c` can render the spinx build slower
because many sources may seem out of date.

It's better to check if we are at the correct revision and
not run *any* git operations if there's nothing to be done
diff --git a/Makefile b/Makefile
@@ -58,7 +58,13 @@ endif
 
 .PHONY: all
 all: ensure_prerequisites
-	git -C $(CPYTHON_PATH) checkout $(CPYTHON_CURRENT_COMMIT)
+	@if [ $(shell git -C $(CPYTHON_PATH) rev-parse HEAD) != $(CPYTHON_CURRENT_COMMIT) ]; then \
+	    echo "Your $(CPYTHON_PATH) repositoy is not at the currect revision"; \
+	    echo "You can run try and run "; \
+	    echo "git -C $(CPYTHON_PATH) checkout $(CPYTHON_CURRENT_COMMIT)"; \
+	    echo "to fix the problem"; \
+	    exit 1; \
+	fi
 	mkdir -p locales/$(LANGUAGE)/LC_MESSAGES/
 	$(CP_CMD) -u --parents *.po */*.po locales/$(LANGUAGE)/LC_MESSAGES/
 	$(MAKE) -C $(CPYTHON_PATH)/Doc/     \
@@ -70,7 +76,6 @@ all: ensure_prerequisites
 	  -D latex_elements.inputenc=       \
 	  -D latex_elements.fontenc='       \
 	  $(MODE)
-	git -C $(CPYTHON_PATH) checkout -
 	@echo "Build success, open file://$(abspath $(CPYTHON_PATH))/Doc/build/html/index.html or run 'make serve' to see them."
 
 
