Refactor conflict resolution to contain git ops within Gitlab::Git

This prepares the codebase for a Gitaly migration. See
https://gitlab.com/gitlab-org/gitaly/issues/553

8 files changed, 314 insertions, 227 deletions

diff --git a/lib/gitlab/conflict/file.rb b/lib/gitlab/conflict/file.rb
index 52f8fe27f3b..2d8a21f4905 100644
--- a/lib/gitlab/conflict/file.rb
+++ b/lib/gitlab/conflict/file.rb
@@ -4,82 +4,26 @@ module Gitlab
       include Gitlab::Routing
       include IconsHelper
 
-      MissingResolution = Class.new(ResolutionError)
-
       CONTEXT_LINES = 3
 
-      attr_reader :merge_file_result, :their_path, :our_path, :our_mode, :merge_request, :repository
+      attr_reader :merge_request, :raw
+
+      delegate :type, :content, :their_path, :our_path, :our_mode, :our_blob, :repository, to: :raw
 
-      def initialize(merge_file_result, conflict, merge_request:)
-        @merge_file_result = merge_file_result
-        @their_path = conflict[:theirs][:path]
-        @our_path = conflict[:ours][:path]
-        @our_mode = conflict[:ours][:mode]
+      def initialize(raw, merge_request:)
+        @raw = raw
         @merge_request = merge_request
-        @repository = merge_request.project.repository
         @match_line_headers = {}
       end
 
-      def content
-        merge_file_result[:data]
-      end
-
-      def our_blob
-        @our_blob ||= repository.blob_at(merge_request.diff_refs.head_sha, our_path)
-      end
-
-      def type
-        lines unless @type
-
-        @type.inquiry
-      end
-
-      # Array of Gitlab::Diff::Line objects
       def lines
         return @lines if defined?(@lines)
 
-        begin
-          @type = 'text'
-          @lines = Gitlab::Conflict::Parser.new.parse(content,
-                                                      our_path: our_path,
-                                                      their_path: their_path,
-                                                      parent_file: self)
-        rescue Gitlab::Conflict::Parser::ParserError
-          @type = 'text-editor'
-          @lines = nil
-        end
+        @lines = raw.lines.nil? ? nil : map_raw_lines(raw.lines)
       end
 
       def resolve_lines(resolution)
-        section_id = nil
-
-        lines.map do |line|
-          unless line.type
-            section_id = nil
-            next line
-          end
-
-          section_id ||= line_code(line)
-
-          case resolution[section_id]
-          when 'head'
-            next unless line.type == 'new'
-          when 'origin'
-            next unless line.type == 'old'
-          else
-            raise MissingResolution, "Missing resolution for section ID: #{section_id}"
-          end
-
-          line
-        end.compact
-      end
-
-      def resolve_content(resolution)
-        if resolution == content
-          raise MissingResolution, "Resolved content has no changes for file #{our_path}"
-        end
-
-        resolution
+        map_raw_lines(raw.resolve_lines(resolution))
       end
 
       def highlight_lines!
@@ -227,9 +171,9 @@ module Gitlab
                                                      new_path: our_path)
       end
 
-      # Don't try to print merge_request or repository.
+      # Don't try to print merge_request.
       def inspect
-        instance_variables = [:merge_file_result, :their_path, :our_path, :our_mode, :type].map do |instance_variable|
+        instance_variables = [:content, :their_path, :our_path, :our_mode, :type].map do |instance_variable|
           value = instance_variable_get("@#{instance_variable}")
 
           "#{instance_variable}=\"#{value}\""
@@ -237,6 +181,16 @@ module Gitlab
 
         "#<#{self.class} #{instance_variables.join(' ')}>"
       end
+
+      private
+
+      def map_raw_lines(raw_lines)
+        raw_lines.map do |raw_line|
+          Gitlab::Diff::Line.new(raw_line[:full_line], raw_line[:type],
+            raw_line[:line_obj_index], raw_line[:line_old],
+            raw_line[:line_new], parent_file: self)
+        end
+      end
     end
   end
 end
diff --git a/lib/gitlab/conflict/file_collection.rb b/lib/gitlab/conflict/file_collection.rb
index 4fedfe8691a..573a953b2aa 100644
--- a/lib/gitlab/conflict/file_collection.rb
+++ b/lib/gitlab/conflict/file_collection.rb
@@ -1,68 +1,29 @@
 module Gitlab
   module Conflict
     class FileCollection
-      ConflictSideMissing = Class.new(StandardError)
-      MissingFiles = Class.new(ResolutionError)
-
-      attr_reader :merge_request, :our_commit, :their_commit, :project, :read_only
-
-      delegate :repository, to: :project
-
-      class << self
-        # We can only write when getting the merge index from the source
-        # project, because we will write to that project. We don't use this all
-        # the time because this fetches a ref into the source project, which
-        # isn't needed for reading.
-        def for_resolution(merge_request)
-          new(merge_request, merge_request.source_project, false)
-        end
-
-        # We don't need to do `with_repo_branch_commit` here, because the target
-        # project always fetches source refs when creating merge request diffs.
-        def read_only(merge_request)
-          new(merge_request, merge_request.target_project, true)
-        end
+      attr_reader :merge_request, :merge
+
+      def initialize(merge_request)
+        source_repo = merge_request.source_project.repository.raw
+        our_commit = merge_request.source_branch_head.raw
+        their_commit = merge_request.target_branch_head.raw
+        target_repo = merge_request.target_project.repository.raw
+        @merge = Gitlab::Git::Merge.new(source_repo, our_commit, target_repo, their_commit)
+        @merge_request = merge_request
       end
 
       def resolve(user, commit_message, files)
-        raise "can't resolve a read-only Conflict File Collection" if read_only
-
-        repository.with_repo_branch_commit(merge_request.target_project.repository.raw, merge_request.target_branch) do
-          rugged = repository.rugged
-
-          files.each do |file_params|
-            conflict_file = file_for_path(file_params[:old_path], file_params[:new_path])
-
-            write_resolved_file_to_index(merge_index, rugged, 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 = {
-            message: commit_message || default_commit_message,
-            parents: [our_commit, their_commit].map(&:oid),
-            tree: merge_index.write_tree(rugged)
-          }
-
-          repository.resolve_conflicts(user, merge_request.source_branch, commit_params)
-        end
-      end
-
-      def merge_index
-        @merge_index ||= repository.rugged.merge_commits(our_commit, their_commit)
+        args = {
+          source_branch: merge_request.source_branch,
+          target_branch: merge_request.target_branch,
+          commit_message: commit_message || default_commit_message
+        }
+        merge.resolve_conflicts(user, files, args)
       end
 
       def files
-        @files ||= merge_index.conflicts.map do |conflict|
-          raise ConflictSideMissing unless conflict[:theirs] && conflict[:ours]
-
-          Gitlab::Conflict::File.new(merge_index.merge_file(conflict[:ours][:path]),
-                                     conflict,
-                                     merge_request: merge_request)
+        @files ||= merge.conflicts.map do |conflict_file|
+          Gitlab::Conflict::File.new(conflict_file, merge_request: merge_request)
         end
       end
 
@@ -81,8 +42,8 @@ module Gitlab
       end
 
       def default_commit_message
-        conflict_filenames = merge_index.conflicts.map do |conflict|
-          "#   #{conflict[:ours][:path]}"
+        conflict_filenames = files.map do |conflict|
+          "#   #{conflict.our_path}"
         end
 
         <<EOM.chomp
@@ -92,31 +53,6 @@ Merge branch '#{merge_request.target_branch}' into '#{merge_request.source_branc
 #{conflict_filenames.join("\n")}
 EOM
       end
-
-      private
-
-      def write_resolved_file_to_index(merge_index, rugged, file, params)
-        if params[:sections]
-          new_file = file.resolve_lines(params[:sections]).map(&:text).join("\n")
-
-          new_file << "\n" if file.our_blob.data.ends_with?("\n")
-        elsif params[:content]
-          new_file = 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)
-        merge_index.conflict_remove(our_path)
-      end
-
-      def initialize(merge_request, project, read_only)
-        @merge_request = merge_request
-        @our_commit = merge_request.source_branch_head.raw.rugged_commit
-        @their_commit = merge_request.target_branch_head.raw.rugged_commit
-        @project = project
-        @read_only = read_only
-      end
     end
   end
 end
diff --git a/lib/gitlab/conflict/parser.rb b/lib/gitlab/conflict/parser.rb
deleted file mode 100644
index e3678c914db..00000000000
--- a/lib/gitlab/conflict/parser.rb
+++ /dev/null
@@ -1,74 +0,0 @@
-module Gitlab
-  module Conflict
-    class Parser
-      UnresolvableError = Class.new(StandardError)
-      UnmergeableFile = Class.new(UnresolvableError)
-      UnsupportedEncoding = Class.new(UnresolvableError)
-
-      # Recoverable errors - the conflict can be resolved in an editor, but not with
-      # sections.
-      ParserError = Class.new(StandardError)
-      UnexpectedDelimiter = Class.new(ParserError)
-      MissingEndDelimiter = Class.new(ParserError)
-
-      def parse(text, our_path:, their_path:, parent_file: nil)
-        validate_text!(text)
-
-        line_obj_index = 0
-        line_old = 1
-        line_new = 1
-        type = nil
-        lines = []
-        conflict_start = "<<<<<<< #{our_path}"
-        conflict_middle = '======='
-        conflict_end = ">>>>>>> #{their_path}"
-
-        text.each_line.map do |line|
-          full_line = line.delete("\n")
-
-          if full_line == conflict_start
-            validate_delimiter!(type.nil?)
-
-            type = 'new'
-          elsif full_line == conflict_middle
-            validate_delimiter!(type == 'new')
-
-            type = 'old'
-          elsif full_line == conflict_end
-            validate_delimiter!(type == 'old')
-
-            type = nil
-          elsif line[0] == '\\'
-            type = 'nonewline'
-            lines << Gitlab::Diff::Line.new(full_line, type, line_obj_index, line_old, line_new, parent_file: parent_file)
-          else
-            lines << Gitlab::Diff::Line.new(full_line, type, line_obj_index, line_old, line_new, parent_file: parent_file)
-            line_old += 1 if type != 'new'
-            line_new += 1 if type != 'old'
-
-            line_obj_index += 1
-          end
-        end
-
-        raise MissingEndDelimiter unless type.nil?
-
-        lines
-      end
-
-      private
-
-      def validate_text!(text)
-        raise UnmergeableFile if text.blank? # Typically a binary file
-        raise UnmergeableFile if text.length > 200.kilobytes
-
-        text.force_encoding('UTF-8')
-
-        raise UnsupportedEncoding unless text.valid_encoding?
-      end
-
-      def validate_delimiter!(condition)
-        raise UnexpectedDelimiter unless condition
-      end
-    end
-  end
-end
diff --git a/lib/gitlab/conflict/resolution_error.rb b/lib/gitlab/conflict/resolution_error.rb
deleted file mode 100644
index 0b61256b35a..00000000000
--- a/lib/gitlab/conflict/resolution_error.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-module Gitlab
-  module Conflict
-    ResolutionError = Class.new(StandardError)
-  end
-end
diff --git a/lib/gitlab/git/conflict_file.rb b/lib/gitlab/git/conflict_file.rb
new file mode 100644
index 00000000000..95a1a9bbe5b
--- /dev/null
+++ b/lib/gitlab/git/conflict_file.rb
@@ -0,0 +1,84 @@
+module Gitlab
+  module Git
+    class ConflictFile
+      attr_reader :content, :their_path, :our_path, :our_mode, :repository
+
+      def initialize(repository, commit_oid, conflict, content)
+        @repository = repository
+        @commit_oid = commit_oid
+        @their_path = conflict[:theirs][:path]
+        @our_path = conflict[:ours][:path]
+        @our_mode = conflict[:ours][:mode]
+        @content = content
+      end
+
+      def lines
+        return @lines if defined?(@lines)
+
+        begin
+          @type = 'text'
+          @lines = Gitlab::Git::ConflictParser.parse(content,
+                                                     our_path: our_path,
+                                                     their_path: their_path)
+        rescue Gitlab::Git::ConflictParser::ParserError
+          @type = 'text-editor'
+          @lines = nil
+        end
+      end
+
+      def type
+        lines unless @type
+
+        @type.inquiry
+      end
+
+      def our_blob
+        # REFACTOR NOTE: the source of `commit_oid` used to be
+        # `merge_request.diff_refs.head_sha`. Instead of passing this value
+        # around the new lib structure, I decided to use `@commit_oid` which is
+        # equivalent to `merge_request.source_branch_head.raw.rugged_commit.oid`.
+        # That is what `merge_request.diff_refs.head_sha` is equivalent to when
+        # `merge_request` is not persisted (see `MergeRequest#diff_head_commit`).
+        # I think using the same oid is more consistent anyways, but if Conflicts
+        # start breaking, the change described above is a good place to look at.
+        @our_blob ||= repository.blob_at(@commit_oid, our_path)
+      end
+
+      def line_code(line)
+        Gitlab::Git::DiffLineCode.generate(our_path, line[:line_new], line[:line_old])
+      end
+
+      def resolve_lines(resolution)
+        section_id = nil
+
+        lines.map do |line|
+          unless line[:type]
+            section_id = nil
+            next line
+          end
+
+          section_id ||= line_code(line)
+
+          case resolution[section_id]
+          when 'head'
+            next unless line[:type] == 'new'
+          when 'origin'
+            next unless line[:type] == 'old'
+          else
+            raise Gitlab::Git::Merge::ResolutionError, "Missing resolution for section ID: #{section_id}"
+          end
+
+          line
+        end.compact
+      end
+
+      def resolve_content(resolution)
+        if resolution == content
+          raise Gitlab::Git::Merge::ResolutionError, "Resolved content has no changes for file #{our_path}"
+        end
+
+        resolution
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/git/conflict_parser.rb b/lib/gitlab/git/conflict_parser.rb
new file mode 100644
index 00000000000..90b03848aee
--- /dev/null
+++ b/lib/gitlab/git/conflict_parser.rb
@@ -0,0 +1,89 @@
+module Gitlab
+  module Git
+    class ConflictParser
+      UnresolvableError = Class.new(StandardError)
+      UnmergeableFile = Class.new(UnresolvableError)
+      UnsupportedEncoding = Class.new(UnresolvableError)
+
+      # Recoverable errors - the conflict can be resolved in an editor, but not with
+      # sections.
+      ParserError = Class.new(StandardError)
+      UnexpectedDelimiter = Class.new(ParserError)
+      MissingEndDelimiter = Class.new(ParserError)
+
+      class << self
+        def parse(text, our_path:, their_path:, parent_file: nil)
+          validate_text!(text)
+
+          line_obj_index = 0
+          line_old = 1
+          line_new = 1
+          type = nil
+          lines = []
+          conflict_start = "<<<<<<< #{our_path}"
+          conflict_middle = '======='
+          conflict_end = ">>>>>>> #{their_path}"
+
+          text.each_line.map do |line|
+            full_line = line.delete("\n")
+
+            if full_line == conflict_start
+              validate_delimiter!(type.nil?)
+
+              type = 'new'
+            elsif full_line == conflict_middle
+              validate_delimiter!(type == 'new')
+
+              type = 'old'
+            elsif full_line == conflict_end
+              validate_delimiter!(type == 'old')
+
+              type = nil
+            elsif line[0] == '\\'
+              type = 'nonewline'
+              lines << {
+                full_line: full_line,
+                type: type,
+                line_obj_index: line_obj_index,
+                line_old: line_old,
+                line_new: line_new
+              }
+            else
+              lines << {
+                full_line: full_line,
+                type: type,
+                line_obj_index: line_obj_index,
+                line_old: line_old,
+                line_new: line_new
+              }
+
+              line_old += 1 if type != 'new'
+              line_new += 1 if type != 'old'
+
+              line_obj_index += 1
+            end
+          end
+
+          raise MissingEndDelimiter unless type.nil?
+
+          lines
+        end
+
+        private
+
+        def validate_text!(text)
+          raise UnmergeableFile if text.blank? # Typically a binary file
+          raise UnmergeableFile if text.length > 200.kilobytes
+
+          text.force_encoding('UTF-8')
+
+          raise UnsupportedEncoding unless text.valid_encoding?
+        end
+
+        def validate_delimiter!(condition)
+          raise UnexpectedDelimiter unless condition
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/git/merge.rb b/lib/gitlab/git/merge.rb
new file mode 100644
index 00000000000..3a0205c17f4
--- /dev/null
+++ b/lib/gitlab/git/merge.rb
@@ -0,0 +1,89 @@
+module Gitlab
+  module Git
+    class Merge
+      ConflictSideMissing = Class.new(StandardError)
+      ResolutionError = Class.new(StandardError)
+
+      def initialize(repository, our_commit, target_repository, their_commit)
+        @repository = repository
+        @our_commit = our_commit.rugged_commit
+        @target_repository = target_repository
+        @their_commit = their_commit.rugged_commit
+      end
+
+      def conflicts
+        @conflicts ||= begin
+          target_index = @target_repository.rugged.merge_commits(@our_commit, @their_commit)
+
+          # We don't need to do `with_repo_branch_commit` here, because the target
+          # project always fetches source refs when creating merge request diffs.
+          target_index.conflicts.map do |conflict|
+            raise ConflictSideMissing unless conflict[:theirs] && conflict[:ours]
+
+            Gitlab::Git::ConflictFile.new(
+              @target_repository,
+              @our_commit.oid,
+              conflict,
+              target_index.merge_file(conflict[:ours][:path])[:data]
+            )
+          end
+        end
+      end
+
+      def resolve_conflicts(user, files, source_branch:, target_branch:, commit_message:)
+        @repository.with_repo_branch_commit(@target_repository, target_branch) do
+          files.each do |file_params|
+            conflict_file = conflict_for_path(file_params[:old_path], file_params[:new_path])
+
+            write_resolved_file_to_index(conflict_file, file_params)
+          end
+
+          unless index.conflicts.empty?
+            missing_files = index.conflicts.map { |file| file[:ours][:path] }
+
+            raise ResolutionError, "Missing resolutions for the following files: #{missing_files.join(', ')}"
+          end
+
+          commit_params = {
+            message: commit_message,
+            parents: [@our_commit, @their_commit].map(&:oid)
+          }
+
+          @repository.commit_index(user, source_branch, index, commit_params)
+        end
+      end
+
+      def conflict_for_path(old_path, new_path)
+        conflicts.find do |conflict|
+          conflict.their_path == old_path && conflict.our_path == new_path
+        end
+      end
+
+      private
+
+      # We can only write when getting the merge index from the source
+      # project, because we will write to that project. We don't use this all
+      # the time because this fetches a ref into the source project, which
+      # isn't needed for reading.
+      def index
+        @index ||= @repository.rugged.merge_commits(@our_commit, @their_commit)
+      end
+
+      def write_resolved_file_to_index(file, params)
+        if params[:sections]
+          resolved_lines = file.resolve_lines(params[:sections])
+          new_file = resolved_lines.map { |line| line[:full_line] }.join("\n")
+
+          new_file << "\n" if file.our_blob.data.ends_with?("\n")
+        elsif params[:content]
+          new_file = file.resolve_content(params[:content])
+        end
+
+        our_path = file.our_path
+
+        index.add(path: our_path, oid: @repository.rugged.write(new_file, :blob), mode: file.our_mode)
+        index.conflict_remove(our_path)
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/git/repository.rb b/lib/gitlab/git/repository.rb
index b705c92d686..0eae8913c49 100644
--- a/lib/gitlab/git/repository.rb
+++ b/lib/gitlab/git/repository.rb
@@ -1096,6 +1096,20 @@ module Gitlab
         Gitlab::Git::Blob.find(self, sha, path) unless Gitlab::Git.blank_ref?(sha)
       end
 
+      def commit_index(user, branch_name, index, options)
+        committer = user_to_committer(user)
+
+        OperationService.new(user, self).with_branch(branch_name) do
+          commit_params = options.merge(
+            tree: index.write_tree(rugged),
+            author: committer,
+            committer: committer
+          )
+
+          create_commit(commit_params)
+        end
+      end
+
       def gitaly_repository
         Gitlab::GitalyClient::Util.repository(@storage, @relative_path, @gl_repository)
       end