Allow setting content for resolutions

When reading conflicts:

1. Add a `type` field. `text` works as before, and has `sections`;
   `text-editor` is a file with ambiguous conflict markers that can only
   be resolved in an editor.
2. Add a `content_path` field pointing to a JSON representation of the
   file's content for a single file.
3. Hitting `content_path` returns a similar datastructure to the `file`,
   but without the `content_path` and `sections` fields, and with a
   `content` field containing the full contents of the file (with
   conflict markers).

When writing conflicts:

1. Instead of `sections` being at the top level, they are now in a
   `files` array. This matches the read format better.
2. The `files` array contains file hashes, each of which must contain:
   a. `new_path`
   b. `old_path`
   c. EITHER `sections` (which works as before) or `content` (with the
      full content of the resolved file).

1 files changed, 20 insertions, 4 deletions

diff --git a/app/services/merge_requests/resolve_service.rb b/app/services/merge_requests/resolve_service.rb
index 19caa038c44..d22a1d3e0ad 100644
--- a/app/services/merge_requests/resolve_service.rb
+++ b/app/services/merge_requests/resolve_service.rb
@@ -1,5 +1,8 @@
 module MergeRequests
   class ResolveService < MergeRequests::BaseService
+    class MissingFiles < Gitlab::Conflict::ResolutionError
+    end
+
     attr_accessor :conflicts, :rugged, :merge_index, :merge_request
 
     def execute(merge_request)
@@ -10,8 +13,16 @@ module MergeRequests
 
       fetch_their_commit!
 
-      conflicts.files.each do |file|
-        write_resolved_file_to_index(file, params[:sections])
+      params[:files].each do |file_params|
+        conflict_file = merge_request.conflicts.file_for_path(file_params[:old_path], file_params[:new_path])
+
+        write_resolved_file_to_index(conflict_file, file_params)
+      end
+
+      unless merge_index.conflicts.empty?
+        missing_files = merge_index.conflicts.map { |file| file[:ours][:path] }
+
+        raise MissingFiles, "Missing resolutions for the following files: #{missing_files.join(', ')}"
       end
 
       commit_params = {
@@ -23,8 +34,13 @@ module MergeRequests
       project.repository.resolve_conflicts(current_user, merge_request.source_branch, commit_params)
     end
 
-    def write_resolved_file_to_index(file, resolutions)
-      new_file = file.resolve_lines(resolutions).map(&:text).join("\n")
+    def write_resolved_file_to_index(file, params)
+      new_file = if params[:sections]
+                   file.resolve_lines(params[:sections]).map(&:text).join("\n")
+                 elsif params[:content]
+                   file.resolve_content(params[:content])
+                 end
+
       our_path = file.our_path
 
       merge_index.add(path: our_path, oid: rugged.write(new_file, :blob), mode: file.our_mode)