Merge branch 'js/fsck-tag-validation' into HEAD

* js/fsck-tag-validation: Make sure that index-pack --strict checks tag objects Add regression tests for stricter tag fsck'ing fsck: check tag objects' headers Make sure fsck_commit_buffer() does not run out of the buffer fsck_object(): allow passing object data separately from the object itself Refactor type_from_string() to allow continuing after detecting an error