Merge branch 'jc/maint-1.6.0-blank-at-eof' (early part) into jc/maint-blank-at-eof

* 'jc/maint-1.6.0-blank-at-eof' (early part):
diff.c: emit_add_line() takes only the rest of the line
diff.c: split emit_line() from the first char and the rest of the line