Code clean-up in the pathspec API.
* bw/pathspec-cleanup:
pathspec: rename prefix_pathspec to init_pathspec_item
pathspec: small readability changes
pathspec: create strip submodule slash helpers
pathspec: create parse_element_magic helper
pathspec: create parse_long_magic function
pathspec: create parse_short_magic function
pathspec: factor global magic into its own function
pathspec: simpler logic to prefix original pathspec elements
pathspec: always show mnemonic and name in unsupported_magic
pathspec: remove unused variable from unsupported_magic
pathspec: copy and free owned memory
pathspec: remove the deprecated get_pathspec function
ls-tree: convert show_recursive to use the pathspec struct interface
dir: convert fill_directory to use the pathspec struct interface
dir: remove struct path_simplify
mv: remove use of deprecated 'get_pathspec()'