Merge remote-tracking branch 'upstream/master' into no-ivar-in-modules

* upstream/master: (1723 commits)
  Resolve "Editor icons"
  Refactor issuable destroy action
  Ignore routes matching legacy_*_redirect in route specs
  Gitlab::Git::RevList and LfsChanges use lazy popen
  Gitlab::Git::Popen can lazily hand output to a block
  Merge branch 'master-i18n' into 'master'
  Remove unique validation from external_url in Environment
  Expose `duration` in Job API entity
  Add TimeCop freeze for DST and Regular time
  Harcode project visibility
  update a changelog
  Put a condition to old migration that adds fast_forward column to MRs
  Expose project visibility as CI variable
  fix flaky tests by removing unneeded clicks and focus actions
  fix flaky test in gfm_autocomplete_spec.rb
  Use Gitlab::Git operations for repository mirroring
  Encapsulate git operations for mirroring in Gitlab::Git
  Create a Wiki Repository's raw_repository properly
  Add `Gitlab::Git::Repository#fetch` command
  Fix Gitlab::Metrics::System#real_time and #monotonic_time doc
  ...

3 files changed, 268 insertions, 0 deletions

diff --git a/lib/gitlab/git/conflict/file.rb b/lib/gitlab/git/conflict/file.rb
new file mode 100644
index 00000000000..fc1595f1faf
--- /dev/null
+++ b/lib/gitlab/git/conflict/file.rb
@@ -0,0 +1,86 @@
+module Gitlab
+  module Git
+    module Conflict
+      class File
+        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::Conflict::Parser.parse(content,
+                                                         our_path: our_path,
+                                                         their_path: their_path)
+          rescue Gitlab::Git::Conflict::Parser::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.diff_line_code(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::Conflict::Resolver::ResolutionError, "Missing resolution for section ID: #{section_id}"
+            end
+
+            line
+          end.compact
+        end
+
+        def resolve_content(resolution)
+          if resolution == content
+            raise Gitlab::Git::Conflict::Resolver::ResolutionError, "Resolved content has no changes for file #{our_path}"
+          end
+
+          resolution
+        end
+      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..3effa9d2d31
--- /dev/null
+++ b/lib/gitlab/git/conflict/parser.rb
@@ -0,0 +1,91 @@
+module Gitlab
+  module Git
+    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)
+
+        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
+end
diff --git a/lib/gitlab/git/conflict/resolver.rb b/lib/gitlab/git/conflict/resolver.rb
new file mode 100644
index 00000000000..df509c5f4ce
--- /dev/null
+++ b/lib/gitlab/git/conflict/resolver.rb
@@ -0,0 +1,91 @@
+module Gitlab
+  module Git
+    module Conflict
+      class Resolver
+        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::Conflict::File.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
+end