Remove preprocessor extension for git blob include processor

It's pretty useless for outside of the custom setup I've had.

lib/asciidoctor/foodogsquared-extensions.rb

@@ -37,7 +37,6 @@ Asciidoctor::Extensions.register do
   include_processor GitLabRawIncludeProcessor
 
   include_processor GitBlobIncludeProcessor
-  preprocessor GitContentBranchAttributePreprocessor
 
   inline_macro WikipediaInlineMacro
 

lib/asciidoctor/git-blob-include-processor/README.adoc

@@ -46,25 +46,11 @@ You can give the following options through `opts` attribute (i.e., `opts="diff,r
 - `reverse` reverses the sides to be compared.
 
 
-== Extra notes
-
-The extension is composed of two parts: an include processor and a preprocessor.
-
-The preprocessor add a document attribute, `doccontentref`, which it gives the Git reference for that content.
-`doccontentref` is the difference between the process working directory (`Dir.pwd`) and the base directory of the content to be converted.
-In case the process working directory is not entirely consistent for several reasons, you could give the attribute `rootdir` as the basis for the comparison.
-As another option, you could also manually set `doccontentref` in case it isn't applicable (i.e., for multilingual sites in Hugo projects).
-
-The include processor also accepts an empty target with the prefix (i.e., `include::git:[]`) as a shorthand for `include::git:{doccontentref}`.
-
-
 == Example usage
 
-The following examples assume that `doccontentref` points to `content/posts/sample`.
-
 - `include::git:HEAD[path=shell.nix]` should transclude the current iteration of `shell.nix`.
 
-- `include::git:{doccontentref}[opts="diff", path=Gemfile]` should include a diff of the Gemfile from `content/posts/sample` branch (assuming that Gemfile has changed).
+- `include::git:v1.0.0[opts="diff", path=Gemfile]` should include a diff of the Gemfile from `content/posts/sample` branch (assuming that Gemfile has changed).
 
 - `include::git:non-existing-rev[opts="diff"]` should result in a warning with the non-existing revision.
 

lib/asciidoctor/git-blob-include-processor/extension.rb

@@ -64,17 +64,3 @@ class GitBlobIncludeProcessor < Asciidoctor::Extensions::IncludeProcessor
     reader
   end
 end
-
-class GitContentBranchAttributePreprocessor < Asciidoctor::Extensions::Preprocessor
-  def process(document, reader)
-    base_dir = Pathname.new(document.base_dir)
-    rootdir = if document.attributes['rootdir'].nil?
-                Dir.pwd
-              else
-                document.attributes['rootdir']
-              end
-
-    document.attributes['doccontentref'] = base_dir.relative_path_from(rootdir).to_s
-    reader
-  end
-end