Merge branch 'rs/pax-extended-header-length-fix'

"git archive" recorded incorrect length in extended pax header in some corner cases, which has been corrected. * rs/pax-extended-header-length-fix: archive-tar: turn length miscalculation warning into BUG archive-tar: use size_t in strbuf_append_ext_header() archive-tar: fix pax extended header length calculation archive-tar: report wrong pax extended header length