Permalink Clash detector clashes on static files

[carbontwelve]

When the clash detector comes across static files such as css/js/img it needs to know that their permalinks are not supposed to be "pretty" (e.g /css/default.css rather than /css/default/index.css).

This is likely a bug in the methods usage of the files getCompiledPermalink method which accepts a boolean. The method should know if the file is static and should therefore not have a "pretty" permalink.

Some linting tools have highlighted that the getCompiledPermalink method appears to break the single responsibility principle and a quick search of its usage within the project show that some times the bool is passed by value and sometimes its defaulted to false. This is likely a hotbed for bugs in the future and needs to be refactored.

An idea would be for getCompiledPermalink to not accept a $pretty argument and instead have this loaded into the File from the projects configuration (the global pretty permalink setting) and over-ridden on a per File basis when it knows it's to be copied (e.g as a static resource via its private toCopy property, or from the files own front matter disabling pretty urls for that file.)

As per usual all of the above requires tests.

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Delving into this I notice that by default upon construction of each File its pretty_permalink data value is set to true.

Refactoring Considerations:

• [x] The getCompiledPermalink method should use the internal pretty_permalink data value instead of a passed boolean.
• [x] Find usages of the Files setToCopy method and ensure they update the File's pretty_permalink data value as well
• [x] Find usages of the Files getCompiledPermalink method and refactor to not pass a value where necessary
• [x] It seems that setting a Files copy flag seems to happen late in execution and should happen before the Compile step - preferably when the File object is first created - refactor as necessary.
• [x] Add unit tests to ensure that static assets such as images, JavaScript and style sheets have their pretty_permalink data value correctly set.

[carbontwelve]

A quick fix for this bug would be to pass $file->isToCopy() to the getCompiledPermalink method within the class detector. But this doesn't actually take into consideration the files true "pretty permalink" setting.

[carbontwelve]

This is fixed by #258