log: refactor: compute the value of last outside of filerevgen
% convert while testing all possible outputs1 files updated, 0 files merged, 0 files removed, 0 files unresolved% check tags are in UTF-8'221c3fdaf24df5f14c0a64c597581e2eacfb47bb branch\xc3\xa9e\n''7a40952c2db29cf00d9e31df3749e98d8a4bdcbf branch\xc3\xa9\n'