Allow relative links to go up one directory level

lib/gitlab/markdown/relative_link_filter.rb

@@ -59,25 +59,44 @@ module Gitlab
       end
 
       def relative_file_path(path)
-        nested_path = build_nested_path(path, context[:requested_path])
+        nested_path = build_relative_path(path, context[:requested_path])
         file_exists?(nested_path) ? nested_path : path
       end
 
-      # Covering a special case, when the link is referencing file in the same
-      # directory.
-      # If we are at doc/api/README.md and the README.md contains relative
-      # links like [Users](users.md), this takes the request
-      # path(doc/api/README.md) and replaces the README.md with users.md so the
-      # path looks like doc/api/users.md.
-      # If we are at doc/api and the README.md shown in below the tree view
-      # this takes the request path(doc/api) and adds users.md so the path
-      # looks like doc/api/users.md
-      def build_nested_path(path, request_path)
+      # Convert a relative path into its correct location based on the currently
+      # requested path
+      #
+      # path         - Relative path String
+      # request_path - Currently-requested path String
+      #
+      # Examples:
+      #
+      #   # File in the same directory as the current path
+      #   build_relative_path("users.md", "doc/api/README.md")
+      #   # => "doc/api/users.md"
+      #
+      #   # File in the same directory, which is also the current path
+      #   build_relative_path("users.md", "doc/api")
+      #   # => "doc/api/users.md"
+      #
+      #   # Going up one level to a different directory
+      #   build_relative_path("../update/7.14-to-8.0.md", "doc/api/README.md")
+      #   # => "doc/update/7.14-to-8.0.md"
+      #
+      # Returns a String
+      def build_relative_path(path, request_path)
         return request_path if path.empty?
         return path unless request_path
 
         parts = request_path.split('/')
         parts.pop if path_type(request_path) != 'tree'
+
+        # Allow for going up one directory
+        if parts.length > 1 && path.start_with?('../')
+          parts.pop
+          path.sub!('../', '')
+        end
+
         parts.push(path).join('/')
       end
 

spec/lib/gitlab/markdown/relative_link_filter_spec.rb

@@ -4,14 +4,16 @@ require 'spec_helper'
 
 module Gitlab::Markdown
   describe RelativeLinkFilter do
-    def filter(doc)
-      described_class.call(doc, {
+    def filter(doc, contexts = {})
+      contexts.reverse_merge!({
         commit:         project.commit,
         project:        project,
         project_wiki:   project_wiki,
         ref:            ref,
         requested_path: requested_path
       })
+
+      described_class.call(doc, contexts)
     end
 
     def image(path)
@@ -75,6 +77,14 @@ module Gitlab::Markdown
           to eq "/#{project_path}/blob/#{ref}/doc/api/README.md"
       end
 
+      it 'rebuilds relative URL for a file in the repo up one directory' do
+        relative_link = link('../api/README.md')
+        doc = filter(relative_link, requested_path: 'doc/update/7.14-to-8.0.md')
+
+        expect(doc.at_css('a')['href']).
+          to eq "/#{project_path}/blob/#{ref}/doc/api/README.md"
+      end
+
       it 'rebuilds relative URL for a file in the repo with an anchor' do
         doc = filter(link('README.md#section'))
         expect(doc.at_css('a')['href']).
@@ -108,8 +118,8 @@ module Gitlab::Markdown
         escaped = Addressable::URI.escape(path)
 
         # Stub these methods so the file doesn't actually need to be in the repo
-        allow_any_instance_of(described_class).to receive(:file_exists?).
-          and_return(true)
+        allow_any_instance_of(described_class).
+          to receive(:file_exists?).and_return(true)
         allow_any_instance_of(described_class).
           to receive(:image?).with(path).and_return(true)