This commit meddles about with both the Colours and the FileExtensions.
Even though all the renderable fields were turned into traits, the FileName struct kept on accessing fields directly on the Colours value instead of calling methods on it. It also did the usual amount of colour misappropriation (such as ‘punctuation’ instead of specifying ‘normal_arrow’)
In preparation for when custom file colours are configurable (any day now), the colourise-file-by-kind functionality (links, sockets, or directories) was separated from the colourise-file-by-name functionality (images, videos, archives). The FileStyle struct already allowed for both to be separate; it was only changed so that a type other than FileExtensions could be used instead, as long as it implements the FileColours trait. (I feel like I should re-visit the naming of all these at some point in the future)
The decision to separate the two means that FileExtensions is the one assigning the colours, rather than going through the fields on a Colours value, which have all been removed. This is why a bunch of arbitrary Styles now exist in filetype.rs.
Because the decision on which colourise-file-by-name code to use (currently just the standard extensions, or nothing if we aren’t colourising) is now determined by the Colours type (instead of being derived), it’s possible to get it wrong. And wrong it was! There was a bug where file names were colourised even though the rest of the --long output wasn’t, and this wasn’t caught by the xtests. It is now.
The FileExtensions in the FileName is now a reference to the one in the original FileStyle, which gets put there in the options module.
This allows the extensions to be derived from the user, somehow, in the future when that part’s done.
Instead of having a File do its own extension checking, create a new type that takes a file and checks *that*. This new type (FileExtensions) is currently empty, but were it to contain values, those values could be used to determine the file’s colour.
The arguments passed to File’s constructor were different from the field names used — these might as well both be the same.
Also, move ext and filename to be File methods to save an import, and add tests.
Also also, by passing a PathBuf in to the constructor directly, we can save one (possibly two) instance/s where we pass in a reference to something we were going to lose ownership of anyway, only to have it basically cloned.
