Merge branch 'mg/more-textconv'

Make "git grep" and "git show" pay attention to --textconv when dealing with blob objects. * mg/more-textconv: grep: honor --textconv for the case rev:path grep: allow to use textconv filters t7008: demonstrate behavior of grep with textconv cat-file: do not die on --textconv without textconv filters show: honor --textconv for blobs diff_opt: track whether flags have been set explicitly t4030: demonstrate behavior of show with textconv