Makefile: Include subdirectories in "make cover" reports
Makefile: Include subdirectories in "make cover" reports

We generate profiling files in all the $(OBJECTS) dirs. Aggregate
results from there, and add them to the corresponding clean target.

Also expand the gcov arguments. Generate reports for things like "x()
|| y()" using --all-blocks, and add --preserve-paths since we're
profiling in subdirectories now.

Signed-off-by: Ævar Arnfjörð Bjarmason <0135fcc047f75af264c800977a73e353c6ba842d@gmail.com>
Reviewed-by: Jonathan Nieder <b57189c5f2fd5b3daf3350a77fde90def1080fa5@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git