Makefile: print what files are not formatted

Move this part from .travis.yml to Makefile.
It's useful to see it always and we generally
don't have lots of logic in the travis file.
Also move list of changed files to the bottom
(that's what one generally sees at console
and at the end of the log).

.travis.yml

@@ -29,11 +29,6 @@ script:
 after_success:
   - curl -s https://codecov.io/bash | bash -s - -y tools/codecov.yml
 
-# If the build fails because some code in not formatted, it's nice to see the diffs after formatting.
-after_failure:
-  - git diff --name-only
-  - git diff
-
 jobs:
   include:
     - stage: fuzzit.dev (regression)

Makefile

@@ -382,4 +382,8 @@ check_links:
 # Check that the diff is empty. This is meant to be executed after generating
 # and formatting the code to make sure that everything is committed.
 check_diff:
-	DIFF="$(shell git diff --name-only)"; test -z "$$DIFF"
+	@if [ "$(shell git diff --name-only)" != "" ]; then \
+		git diff; \
+		echo -e "\n\nSome files are not formatted/regenerated (include them into commit):"; \
+		git diff --name-only; \
+	fi