Merge branch 'tr/coverage' into maint

The test coverage framework was left broken for some time.

* tr/coverage:
  coverage: build coverage-untested-functions by default
  coverage: set DEFAULT_TEST_TARGET to avoid using prove
  coverage: do not delete .gcno files before building
  coverage: split build target into compile and test

Makefile

@@ -2463,7 +2463,7 @@ profile-clean:
 	$(RM) $(addsuffix *.gcda,$(addprefix $(PROFILE_DIR)/, $(object_dirs)))
 	$(RM) $(addsuffix *.gcno,$(addprefix $(PROFILE_DIR)/, $(object_dirs)))
 
-clean: profile-clean
+clean: profile-clean coverage-clean
 	$(RM) *.o block-sha1/*.o ppc/*.o compat/*.o compat/*/*.o xdiff/*.o vcs-svn/*.o \
 		builtin/*.o $(LIB_FILE) $(XDIFF_LIB) $(VCSSVN_LIB)
 	$(RM) $(ALL_PROGRAMS) $(SCRIPT_LIB) $(BUILT_INS) git$X
@@ -2544,29 +2544,34 @@ check-builtins::
 
 ### Test suite coverage testing
 #
-.PHONY: coverage coverage-clean coverage-build coverage-report
+.PHONY: coverage coverage-clean coverage-compile coverage-test coverage-report
+.PHONY: coverage-clean-results
 
 coverage:
-	$(MAKE) coverage-build
-	$(MAKE) coverage-report
+	$(MAKE) coverage-test
+	$(MAKE) coverage-untested-functions
 
 object_dirs := $(sort $(dir $(OBJECTS)))
-coverage-clean:
+coverage-clean-results:
 	$(RM) $(addsuffix *.gcov,$(object_dirs))
 	$(RM) $(addsuffix *.gcda,$(object_dirs))
-	$(RM) $(addsuffix *.gcno,$(object_dirs))
 	$(RM) coverage-untested-functions
 	$(RM) -r cover_db/
 	$(RM) -r cover_db_html/
 
+coverage-clean: coverage-clean-results
+	$(RM) $(addsuffix *.gcno,$(object_dirs))
+
 COVERAGE_CFLAGS = $(CFLAGS) -O0 -ftest-coverage -fprofile-arcs
 COVERAGE_LDFLAGS = $(CFLAGS)  -O0 -lgcov
 GCOVFLAGS = --preserve-paths --branch-probabilities --all-blocks
 
-coverage-build: coverage-clean
+coverage-compile:
 	$(MAKE) CFLAGS="$(COVERAGE_CFLAGS)" LDFLAGS="$(COVERAGE_LDFLAGS)" all
+
+coverage-test: coverage-clean-results coverage-compile
 	$(MAKE) CFLAGS="$(COVERAGE_CFLAGS)" LDFLAGS="$(COVERAGE_LDFLAGS)" \
-		-j1 test
+		DEFAULT_TEST_TARGET=test -j1 test
 
 coverage-report:
 	$(QUIET_GCOV)for dir in $(object_dirs); do \