Add "scheme" to fern core instance

Author: lambdalisue

autoload/fern/internal/core.vim

@@ -14,8 +14,10 @@ function! fern#internal#core#new(url, provider, ...) abort
         \ 'comparator': g:fern#comparator,
         \}, a:0 ? a:1 : {},
         \)
+  let scheme = fern#fri#parse(a:url).scheme
   let root = fern#internal#node#root(a:url, a:provider)
   let fern = {
+        \ 'scheme': scheme,
         \ 'source': s:CancellationTokenSource.new(),
         \ 'provider': a:provider,
         \ 'renderer': s:get_renderer(options.renderer),

doc/fern-develop.txt

@@ -304,6 +304,7 @@ VARIABLE				*fern-develop-helper-variable*
 .fern
 	A fern instance which has the following attributes:
 
+	"scheme"	A scheme name used to determine "provider"
 	"source"	A cancellation token source to cancel requests
 	"provider"	A provider instance for the fren tree
 	"renderer"	A renderer instance to sort nodes

test/fern/internal/core.vimspec

@@ -9,6 +9,7 @@ Describe fern#internal#core
   Describe #new()
     It returns a fern instance of given url and provider
       let fern = fern#internal#core#new('debug:///', provider)
+      Assert KeyExists(fern, 'scheme')
       Assert KeyExists(fern, 'source')
       Assert KeyExists(fern, 'provider')
       Assert KeyExists(fern, 'comparator')