Update git blob include processor

- Update `path` to accept semicolon-delimited list of paths when `diff`
  option is used.
- Add `other` option for diffs.

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

@@ -24,10 +24,14 @@ If the resulting operation ends in an error (i.e., non-existing revision, file,
 == Attributes
 
 - `path` is the filepath to be retrieved from the revision.
+When used with `diff`, it changes into a semicolon-delimited (`;`) list of files to make diffs with multiple files.
 
 - `context-lines` is the number of surrounding lines for the diff.
 This is only effective if `diff` option is given.
 
+- `other` is the other commit to be compared with.
+This is only effective if `diff` option is given.
+
 There's also a couple of link:https://docs.asciidoctor.org/asciidoc/latest/attributes/options/[options] for this component.
 You can give the following options through `opts` attribute (i.e., `opts="diff,reverse"`).
 

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

@@ -19,11 +19,16 @@ class GitBlobIncludeProcessor < Asciidoctor::Extensions::IncludeProcessor
       if attrs.key? 'diff-option'
         options = {}
 
-        options[:paths] = [attrs['path']] if attrs.key? 'path'
+        options[:paths] = attrs['path'].split(';') if attrs.key? 'path'
         options[:context_lines] = attrs['context-lines'] if attrs.key? 'context-lines'
         options[:reverse] = true if attrs.key? 'reverse-option'
 
+        if attrs.key? 'other'
+          other = repo.rev_parse attrs['other'] || nil
+          reader.push_include git_object.diff(other, **options).patch
+        else
           reader.push_include git_object.diff(**options).patch
+        end
       else
         inner_entry = case git_object.type
                       when :blob