Merge branch 'tg/add-chmod+x-fix'

"git add --chmod=+x <pathspec>" added recently only toggled the executable bit for paths that are either new or modified. This has been corrected to flip the executable bit for all paths that match the given pathspec. * tg/add-chmod+x-fix: t3700-add: do not check working tree file mode without POSIXPERM t3700-add: create subdirectory gently add: modify already added files when --chmod is given read-cache: introduce chmod_index_entry update-index: add test for chmod flags