hg_git_repository.rb 36.8 KB
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# Index of the line in lines matching a given regexp
def match_idx(lines, rx)
  lines.each_with_index do |line, i|
    return i if rx.match(line)
  end
  nil
end

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module Gitlab
  module Mercurial
    class HgGitRepository < Gitlab::Git::Repository
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      include Gitlab::Popen
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      MergeError = Class.new(StandardError)
      HgError = Class.new(StandardError)
      InvalidHgSetting = Class.new(StandardError)
      HgRevisionError = Class.new(StandardError)
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      # In general, GitLab expects `multi_action` to raise IndexError,
      # so let's subclass it.
      ActionError = Class.new(Gitlab::Git::Index::IndexError)
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      DEFAULT_HGRC = [
        "# This is the specific configuration for this repository",
        "# You may modify it freely at your will.",
        "#",
        "# By default, it includes the configuration from the enclosing group",
        "# but all the settings defined in the present file will take precedence",
        "# as long as they are below the %include line",
        "# You may also remove the %include line altogether if you prefer.",
        "",
        "# group-level configuration",
        "%include <GROUP_HGRC_RPATH>",
        ""].join("\n").freeze

      DEFAULT_SUBGROUP_HGRC = [
        "# This is the Mercurial configuration for this subgroup.",
        "# You may modify it freely at your will.",
        "#",
        "# By default, it includes the configuration from the enclosing",
        "# group, but all the settings defined in the present file will",
        "# take precedence as long as they are below the %include line",
        "# You may also remove the %include line altogether if you prefer.",
        "",
        "# enclosing group configuration",
        "%include ../hgrc",
        ""].join("\n").freeze

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      def initialize(*args)
        super(*args)
        @hg_relative_path = relative_path.sub(/\.git$/, '.hg')
        @hg_storage_root = Gitlab.config.repositories.storages.fetch(storage).hg_disk_path
        @hgpath = File.join(@hg_storage_root, @hg_relative_path)
      end

      # Mercurial path will stay until HGitaly is ready
      def hg_full_path
        @hgpath
      end

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      def create_repository(**named_args)
        # at the time being all named_args are Mercurial specific. Still,
        # passing explicitely is more future proof
        super(**named_args)
        create_hg_repository(**named_args)
      end

      # Create the Mercurial repository only
      #
      # This is what a FS based native Mercurial class would do
      #
      # - namespace_fs_path: the path of the directory for the parent
      #                      namespace config files
      # - in_subgroup: true is the parent namespace is a subgroup
      def create_hg_repository(namespace_fs_path:, in_subgroup:)
        Rails.logger.info(
          "Creating Mercurial repository at #{@hg_relative_path} "\
          "namespace path=#{namespace_fs_path} "\
          "in_subgroup: #{in_subgroup}")
        begin
          out, status = popen(
                 [Gitlab.config.mercurial.bin_path, "init", @hgpath],
                 # Rails.root can be a Mercurial repo, that can lead to
                 # complications. Let's run from a path that's very unlikely
                 # to be one:
                 @hg_storage_root,
                 { 'HGRCPATH' => Gitlab::Mercurial.hgrc_path,
                 })
          if status != 0
            raise HgError, "Could not execute `hg init` for #{@hgpath}: #{out}"
          end

          File.write(File.join(@hgpath, '.hg', 'hgrc'),
                     DEFAULT_HGRC.sub('<GROUP_HGRC_RPATH>',
                                      hgrc_inherit_path(namespace_fs_path)))

          if in_subgroup
            ns_path = Pathname(@hg_storage_root).join(namespace_fs_path)
            ns_hgrcf = ns_path.join('hgrc')
            unless File.exist?(ns_hgrcf)
              FileUtils.mkdir_p(ns_path)
              File.write(ns_hgrcf, DEFAULT_SUBGROUP_HGRC)
            end
          end
        end
        true
      rescue => err
        Rails.logger.error("Failed to add Mercurial repository for #{storage}/#{name}: #{err}")
        false
      end

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      def hg_sha_map
        @git_sha_map = nil unless @hg_sha_map
        # Get the entries of the git-mapfile and store them in a git => hg Hash
        @hg_sha_map ||= File.open(File.join(@hgpath, '.hg', 'git-mapfile')) do |f|
          f.map do |line|
            line.match(/^([0-9a-f]{40}) ([0-9a-f]{40})\n$/) do |match|
              [match[1], match[2]]
            end
          end
          .to_h
        end
      end

      def git_sha_map
        # Reverse the entries, so that it is a hg => git Hash
        @git_sha_map ||= hg_sha_map.to_a.map {|x| x.reverse }.to_h
      end

      def sha_from_hgsha(hgsha)
        return nil unless exists?

        git_sha_map[hgsha]
      end

      def hgsha_from_sha(sha)
        return nil unless exists?

        hg_sha_map[sha]
      end

      def hg_git_invalidate_maps!
        @git_sha_map = nil
        @hg_sha_map = nil
      end

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      # Retrieve the Mercurial SHA from a symbolic revision
      #
      # `path` can be specified to use something else than
      # the main repository path, typically a temporary working dir
      # obtained through `hg share`, hence taking advantage of working dir
      # revisions (`.`)
      def hgsha_from_rev(hgrev, path = nil)
        hg_env = {'HGRCPATH' => Gitlab::Mercurial.hgrc_path,
                 }

        path = @hgpath if path.nil?
        sha, status = popen([Gitlab.config.mercurial.bin_path,
                             'log', '--limit', '1', '-r', hgrev,
                             '-T', '{node}'],
                            path, hg_env)
        if status != 0
          raise HgRevisionError,
                "Could not find changeset #{hgrev} in #{@hgpath}"
        end
        sha
      end

      # Find the named branch of a Mercurial changeset
      def hg_changeset_branch(hgsha)
        out, status = popen([Gitlab.config.mercurial.bin_path,
                             'log', '-r', hgsha, '-T', '{branch}'],
                            @hgpath,
                            {'HGRCPATH' => Gitlab::Mercurial.hgrc_path,
                            })
        if status != 0
          raise HgError, "Could not get hg branch of changeset #{hgsha}: #{out}"
        end
        out.strip
      end

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      def parse_gitlab_branch_for_hg(gitlab_branch)
        if gitlab_branch.start_with?('branch/')
          [gitlab_branch[7..], nil]
        elsif gitlab_branch.start_with?('topic/')
          branch, _slash, topic = gitlab_branch[6..].rpartition('/')
          [branch, topic]
        else
          raise StandardError, "bookmarks not supported (got #{gitlab_branch})"
        end
      end

      def hg_branchmap_branch(hg_branch, topic)
        if topic.nil?
          hg_branch
        else
          "#{hg_branch}:#{topic}"
        end
      end

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      # Return a suitable environment for write operations (merge etc.)
      def hg_env_for_write(user)
        {
          # `name` and `email` are as in `committer` (which
          # does not have `username`) but the purpose here is
          # different: we want to pass them
          # along regardless of what should be a commit authorship.
          # Of that later information would change for any reason
          # these would still be directly linked to authenticated
          # user info
          'HEPTAPOD_SKIP_ALL_GITLAB_HOOKS' => "yes",
          'HEPTAPOD_USERINFO_ID' => user.id.to_s,
          'HEPTAPOD_USERINFO_USERNAME' => user.username,
          'HEPTAPOD_USERINFO_NAME' => user.name,
          'HEPTAPOD_USERINFO_EMAIL' => user.email,
          'GL_REPOSITORY' => @gl_repository,  # for Heptapod 0.13
          # for Heptapod 0.12:
          'HEPTAPOD_PROJECT_ID' => @gl_repository.rpartition('-')[-1],
          'HEPTAPOD_PROJECT_PATH' => self.name.chomp('.git'),
          # TODO won't work on hashed storage
          'HEPTAPOD_PROJECT_NAMESPACE_FULL_PATH' => @relative_path.rpartition('/')[0],
          'HGUSER' => nil,
          'HGRCPATH' => Gitlab::Mercurial.hgrc_path
        }
      end

      def hg_prepare_user_encoding(hg_env, user, message)
        committer = Gitlab::Git.committer_hash(email: user.email, name: user.name)
        username = "#{committer[:name]} <#{committer[:email]}>"
        # we take the encoding from one of the two strings
        # it would be very surprising for them to differ, and
        # hg couldn't cope with that anyway (usually, it's UTF8)
        encname = username.encoding.name
        hg_env["HGENCODING"] = encname

        if message.encoding.name != encname
          # this would be very suprising, but if it ever happens
          # people debugging the case will be glad to have this log
          # (Mercurial could cope with that only in cases one of the
          # strings is actually pure ASCII (decoding is trivial)
          Rails.logger.error("Encoding of commit message #{message.encoding.name} differs "\
                             "from user name's #{encname}")
        end
        username
      end

      # Publish a changeset
      #
      # The given `user` information will be passed over to Mercurial
      # in the usual environment variables
      def hg_changeset_publish(user, hgsha, notify_gitlab: false)
        env = hg_env_for_write(user)
        env.delete('HEPTAPOD_SKIP_ALL_GITLAB_HOOKS') if notify_gitlab
        out, status = popen([Gitlab.config.mercurial.bin_path,
                             'phase', '--public', '-r', hgsha],
                            @hgpath, env)
        raise HgError, "Could not publish changeset #{hgsha}: #{out}" unless status.zero?
      end

      # Perform a Mercurial commit
      #
      # `path` - the working directory path, typically obtained with `hg share`
      # `username` - used as `ui.username`
      # `env` - preparred Hash of environment variables
      #
      # returns Mercurial SHA
      def hg_commit(path, username, message, env, add_remove = false)
        cmd = [Gitlab.config.mercurial.bin_path, 'commit',
         '--config', 'ui.username=' + username,
         '-m', message,
              ]
        cmd.append('--addremove') if add_remove
        output, status = popen(cmd, path, env)
        raise HgError, "Could not commit: #{output}"  if status != 0

        hgsha_from_rev('.', path)
      end

      # Create an independent working directory
      #
      # this relies onto `hg share`, of which that's one of the main use
      # cases.
      #
      # `update_rev`: revision to update the new working directoy to
      #
      # returns path to the working directory
      def hg_new_workdir(update_rev)
        share_path = @hgpath + "tmp" + SecureRandom.hex

        hg_exe = Gitlab.config.mercurial.bin_path
        env = { 'HGRCPATH' => Gitlab::Mercurial.hgrc_path }
        output, status = popen([hg_exe, 'share',
                                @hgpath, share_path,
                                '--noupdate', '--bookmarks'],
                               nil, env)
        raise HgError, "Could not share repo at #{@hgpath} to #{share_path}: #{output}" if status != 0

        unless update_rev.nil?
          output, status = popen([hg_exe, 'up', update_rev], share_path, env)
          raise HgError, "Could not update shared repo to #{update_rev}: #{output}" if status != 0
        end
        share_path
      end

      # Produce a Mercurial merge changeset
      #
      # This method works with Mercurial SHAs only, and performs `merge` and `commit` in
      # insulation, by working in a temporary repository created with `share`.
      #
      # For `hg_git` repositories, the resulting writes to the Git repository are
      # protected by the Mercurial store lock, which is always held on the share source.
      def hg_merge_changeset(user, source_hgsha, target_hgsha, message,
                             simulate = false)
        logprefix = "hg_merge_changeset "
        logprefix += "simulation " if simulate
        logprefix += "for #{@relative_path} #{source_hgsha} into #{target_hgsha}"
        logger = Rails.logger  # could need to be adapted for gitaly-ruby (see initialize())
        hg_exe = Gitlab.config.mercurial.bin_path
        hg_env = if user.nil?
                   # TODO time to have a method for minimal hg_env
                   {'HGRCPATH' => Gitlab::Mercurial.hgrc_path}
                 else
                   hg_env_for_write(user)
                 end

        share_path = nil
        begin
          share_path = hg_new_workdir(target_hgsha)
          logger.info("#{logprefix} calling #{hg_exe} merge -r #{source_hgsha}")
          output, status = popen([hg_exe, 'merge',
                                  '-t', 'internal:merge3',
                                  '-r', source_hgsha
                                 ],
                                 share_path, hg_env)
          if status != 0
            raise MergeError, "Could not merge hg #{source_hgsha} onto hg #{target_hgsha}: #{output}"
          end

          # note for non-rubyists: 'ensure' condition is still executed
          # with early returns.
          return if simulate

          username = hg_prepare_user_encoding(hg_env, user, message)
          commit_hgsha = hg_commit(share_path, username, message, hg_env)
          logger.info("#{logprefix} merge done, final changeset is #{commit_hgsha}")
        ensure
          FileUtils.rm_rf(share_path) unless share_path.nil?
        end
        commit_hgsha
      end

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      def merge(user, source_sha, target_branch, message)
        logprefix = "hg_merge for #{@relative_path} "\
                    "source_sha=#{source_sha} target_branch=#{target_branch}"
        logger = Rails.logger  # could need to be adapted for gitaly-ruby (see initialize())
        logger.info("#{logprefix} starting")

        begin
          target_sha = find_branch(target_branch).target

          raise 'Invalid merge target' unless target_sha
          raise 'Invalid merge source' unless source_sha

          begin
            source_hgsha = hgsha_from_sha(source_sha)
            target_hgsha = hgsha_from_sha(target_sha)
            begin
              target_hg_branch = hg_changeset_branch(target_hgsha)
              source_hg_branch = hg_changeset_branch(source_hgsha)
            rescue HgError => e
              raise MergeError, e.message
            end

            with_merge_changeset =
              (target_hg_branch != source_hg_branch) || !(ancestor?(target_sha, source_sha))

            result_hgsha =
              if with_merge_changeset
                hg_merge_changeset(user, source_hgsha, target_hgsha, message)
              else
                logger.info("#{logprefix} this is a merge without merge changeset")
                source_hgsha
              end

            logger.info("#{logprefix} publishing changeset #{result_hgsha}")
            begin
              hg_changeset_publish(user, result_hgsha, notify_gitlab: true)
            rescue HgError => e
              raise MergeError, e.message
            end

            logger.info("#{logprefix} merge done, final changeset is #{result_hgsha}")
          end

          hg_git_invalidate_maps!
          commit_id = sha_from_hgsha result_hgsha

          yield commit_id

          Gitlab::Git::OperationService::BranchUpdate.new(commit_id, false, false)

        end
      rescue Gitlab::Git::CommitError # when merge_index.conflicts?
        nil
      end

      def can_be_merged?(source_sha, target_branch)
        logprefix = "Mercurial.can_be_merged? for #{@relative_path} "\
                    "source_sha=#{source_sha} target_branch=#{target_branch}"
        logger = Rails.logger  # could need to be adapted for gitaly-ruby (see initialize())

        return false unless source_sha

        target_sha = find_branch(target_branch)&.target
        if target_sha.nil?
          logger.warn("#{logprefix} could not resolve Git branch #{target_branch}")
          return false
        end
        if ancestor?(target_sha, source_sha)
          # always doable: true fast forward or merge changeset only
          # involving metadata (e.g., branch change)
          logger.info("#{logprefix} is mergeable (direct ancestor)")
          return true
        end

        source_hgsha = hgsha_from_sha(source_sha)
        target_hgsha = hgsha_from_sha(target_sha)
        if source_hgsha.nil?
          logger.warn(
            "#{logprefix} could not find Hg changeset for source Git commit #{source_sha}")
          return false
        end
        if target_hgsha.nil?
          logger.warn(
            "#{logprefix} could not find Hg changeset for target Git commit #{target_sha}")
          return false
        end

        begin
          hg_merge_changeset(nil, source_hgsha, target_hgsha, nil, true)
          logger.info("#{logprefix} is mergeable (true merge)")
          true
        rescue HgError, MergeError => e
          logger.info("#{logprefix} not mergeable: #{e.class}, #{e.message}")
          false
        end
      end

      def ff_merge(user, source_sha, target_branch)
        source_hgsha = hg_sha_map[source_sha]
        raise ArgumentError, 'Invalid merge target' unless find_branch(target_branch).target

        hg_branch = begin
                      hg_changeset_branch(source_hgsha)
                    rescue HgError => e
                      raise MergeError, e.message
                    end

        if target_branch != "branch/" + hg_branch
          # TODO how to return the proper error 406 seen from API?
          raise MergeError, "Being on branch #{hg_branch}, "\
                            "changeset #{source_hgsha} cannot be published "\
                            "within #{target_branch}"
        end

        begin
          hg_changeset_publish(user, source_hgsha, notify_gitlab: true)
        rescue HgError => e
          raise MergeError, e
        end

        Gitlab::Git::OperationService::BranchUpdate.new(source_sha, false, false)
      rescue Gitlab::Git::CommitError
        nil
      end

      # Squash a linear range of changesets.
      #
      # In typical usage (merge requests), start_sha is ill-named:
      # it is the head of the target branch (perhaps not really the head any
      # more).
      def squash(user, squash_id, branch:, start_sha:, end_sha:, author:, message:)
        logprefix = "hg_squash "
        logger = Rails.logger
        hg_exe = Gitlab.config.mercurial.bin_path
        hg_env = hg_env_for_write(user)

        start_hgsha = hgsha_from_sha(start_sha)
        end_hgsha = hgsha_from_sha(end_sha)
        username = hg_prepare_user_encoding(hg_env, author, message)

        share_path = nil
        begin
          # TODO: gracinet not 100% sure we need a workdir, but I don't see
          # an explicit "inmemory" option as there is for `hg rebase`

          # If we update to target_hgsha, then the fold will look like
          # an extra head and be rejected (probably because it is kept active by being the
          # working dir parent). Let's not update anywhere.
          share_path = hg_new_workdir(nil)

          revset = "ancestor(#{start_hgsha}, #{end_hgsha})::#{end_hgsha} "\
                   "- ancestor(#{start_hgsha}, #{end_hgsha})"
          logger.info("#{logprefix} calling `hg squash --exact` "\
                      "on revset `#{revset}` #{message.nil?} for #{username}")
          # Note that hg fold --exact will fail unless the revset is
          # "an unbroken linear chain". That fits the idea of a Merge Request
          # neatly, and should be unsuprising to users: it's natural to expect
          # squashes to stay simple.
          # In particular, if there's a merge of a side topic, it will be
          # unsquashable.
          # `allowunstable=no` protects us against all instabilities,
          # in particular against orphaning dependent topics.
          output, status = popen(
                    [hg_exe, 'fold', '--exact',
                     '-r', revset,
                     '-m', message,
                     '-u', username,
                     '--config', 'experimental.evolution.allowunstable=no',
                    ],
                    share_path, hg_env)
          if status != 0
            raise HgError, "Could not fold revset `#{revset}` Error: #{output}"
          end
          logger.info("#{logprefix} squash done, finding successor")
          output, status = popen(
                    [hg_exe, 'hpd-unique-successor', '-r', end_hgsha],
                    share_path, hg_env)
          if status != 0
            raise HgError, "Could not retrieve folded changeset "\
                           "(successor of #{end_hgsha})"
          end
          squash_hgsha = output.strip
          logger.info("#{logprefix} squash successor changeset #{squash_hgsha}")

          hg_git_invalidate_maps!
          sha_from_hgsha(squash_hgsha)
        ensure
          FileUtils.rm_rf(share_path) unless share_path.nil?
        end
      end

      # Mercurial squashes are atomic. We can pretend there's no squash
      # in progress.
      #
      # Actually at this point, reading the resulting changeset is not,
      # but it doesn't matter much: there's no risk of repo corruption.
      def squash_in_progress?(squash_id)
        false
      end

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      # Pull a given revision from URL forcing topic on all new changesets
      #
      # Return:
      #   [full node, branch name, topic name]
      #
      # It is not guaranteed that the returned full node carries the given
      # topic. This happens for instance if it was already known and public.
      # In that case, the returned topic is empty
      def pull_force_topic(url, hgsha, topic)
        # necessary to amend changesets
        # TODO do better and think of encoding, as well
        hg_env = {'HGUSER' => 'Heptapod system',
                  'HEPTAPOD_SKIP_ALL_GITLAB_HOOKS' => 'yes',
                  'HGRCPATH' => Gitlab::Mercurial.hgrc_path,
                 }
        hg_exe = Gitlab.config.mercurial.bin_path
        _output, status = popen(
                  [hg_exe,
                   'pull-force-topic', '-q', '-r', hgsha, topic, url,
                   '--config', 'experimental.single-head-per-branch=no',
                   '--config', 'topic.publish-bare-branch=no',
                   '--config', 'experimental.hg-git.accept-slash-in-topic-name=yes',
                   '--config', 'experimental.hg-git.bookmarks-on-named-branches= yes',],
                  @hgpath, hg_env
                )

        if status == 1
          query_rev = hgsha
        elsif status != 0
          raise StandardError, "Could not pull-force-topic #{hgsha} from #{url}"
        else
          query_rev = topic
        end

        hg_git_invalidate_maps!
        node_branch, status = popen(
                       [hg_exe, 'log', '-T', '{node}:{branch}:{topic}',
                        '-r', query_rev],
                       @hgpath, hg_env)
        if status != 0
          raise HgRevisionError, "Could not log revision #{query_rev}"
        end
        node_branch.split(':')
      end

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      # perform multiple write actions in the repository in a single commit
      #
      # typically multiple file writes or renames, followed by a commit
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      #
      # actions details (should be the same as with Git::Repository):
      #
      # - create: ensures there's not a file at the same `file_path` already
      #           and take care of intermediate directories
      # - update: ensures the file at `file_path` already exists.
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      def multi_action(user, branch_name:, message:, actions:,
        author_email: nil, author_name: nil,
        start_branch_name: nil, start_sha: nil, start_repository: self,
        force: false)
        logprefix = "hg_multi_action for #{@relative_path} "\
                    "start_branch_name=#{start_branch_name} branch_name=#{branch_name}"
        logger = Rails.logger  # could need to be adapted for gitaly-ruby (see initialize())
        logger.info("#{logprefix} starting")

        hg_exe = Gitlab.config.mercurial.bin_path
        hg_env = hg_env_for_write(user)

        committer = Gitlab::Git.committer_hash(email: user.email, name: user.name)
        username = "#{committer[:name]} <#{committer[:email]}>"
        # we take the encoding from one of the two strings
        # it would be very surprising for them to differ, and
        # hg couldn't cope with that anyway (usually, it's UTF8)
        encname = username.encoding.name
        hg_env["HGENCODING"] = encname

        branch_creating = !branch_exists?(branch_name)
        repo_creating = exists?

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        start_branch_name ||= branch_name

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        share_path = nil
        begin
          start_hg_branch, start_topic = parse_gitlab_branch_for_hg(start_branch_name)
          # using the branchmap notation to perform just one update
          start_hg = if empty?
                       nil
                     else
                       hg_branchmap_branch(start_hg_branch, start_topic)
                     end
          share_path = hg_new_workdir(start_hg)

          hg_branch, topic = parse_gitlab_branch_for_hg(branch_name)
          if hg_branch != start_hg_branch
            # doing this inconditionally would be more that just a waste of
            # resources, it could reset the topic
            output, status = popen([hg_exe, 'branch', hg_branch], share_path, hg_env)
            if status != 0
              raise HgError, "Could not switch working dir to branch #{hg_branch}: #{output}"
            end
          end

          if topic != start_topic
            if topic.nil?
              output, status = popen([hg_exe, 'topic', '--clear'], share_path, hg_env)
              if status != 0
                raise HgError, "Could not clear topic: #{output}"
              end
            else
              output, status = popen([hg_exe, 'topic', topic], share_path, hg_env)
              if status != 0
                raise HgError, "Could not set topic to #{topic}: #{output}"
              end
            end
          end
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          logger.info("#{logprefix} Setup done, ready to execute actions "\
                      "in workdir #{share_path}")
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          actions.each do |action|
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            if !action[:file_path]
              raise HgError, "All current actions need a file_path argument"
            end

            file_path = File.join(*action[:file_path].split('/'))
            abspath = File.join(share_path, file_path)

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            logger.info(
              "#{logprefix} Performing '#{action[:action]}' for #{file_path}")
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            case action[:action]
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            when :create
              if File.exists?(abspath)
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                raise ActionError, "A file with this name already exists"
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              end
              parent_abspath = File.split(abspath)[0]
              if File.file?(parent_abspath)
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                raise ActionError, "A file with same name as parent directory "\
                                  "already exists."
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              end
              FileUtils.mkdir_p(parent_abspath)
              # File.write uses text mode, which forces conversion to
              # Encoding.external_encoding ('UTF-8') and gives an error.
              # On the other hand, a file explicitely open in binary mode
              # is happy to receive an UTF-8 string
              File.open(abspath, "wb") do |f|
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                f.write(action[:content])
              end
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            when :update
              unless File.file?(abspath)
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                raise ActionError, "A file with this name doesn't exist"
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              end
              File.write(abspath, action[:content])
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            when :create_dir
              if File.file?(abspath)
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                raise ActionError, "A file with this name already exists "
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              end
              if File.directory?(abspath)
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                raise ActionError, "A directory with this name already exists"
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              end
              FileUtils.mkdir_p(abspath)
              File.write(File.join(abspath, '.hg_keep'), '')
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            when :move
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              previous_path = File.join(action[:previous_path].split('/'))
              new_path = file_path
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              unless File.exists?(File.join(share_path, previous_path))
                raise ActionError, "A file with this name doesn't exist"
              end
              if File.exists?(abspath)
                raise ActionError, "A file with this name already exists"
              end
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              # hg mv will take care of creating parent dir if needed
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              output, status = popen([hg_exe, 'mv', previous_path, new_path], share_path, hg_env)
              # TODO should check if file is tracked and do a simple `mv` if not
              if status != 0
                raise HgError, "Could not `hg mv #{previous_path} #{new_path}`: #{output}"
              end
            when :delete
              # Let's support chains of actions that could be simplified (use-case: generated).
              # We're currently never just 'adding' a file, but let's be future proof.
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              unless File.exists?(abspath)
                raise ActionError, "A file with this name doesn't exist"
              end
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              output, status = popen([hg_exe, 'rm', '-f', file_path], share_path, hg_env)
              if ![0, 1].include?(status)  # status 1 happens with untracked files
                raise HgError, "Could not `hg rm -f #{file_path}`: #{output}"
              end
              # needed if the rm was actually just a forget:
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              FileUtils.rm_f(abspath)
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            else
              raise HgError,  "Notimplemented action #{action}"
            end
          end

          if !message.nil? && message.encoding.name != encname
            # this would be very suprising, but if it ever happens
            # people debugging the case will be glad to have this log
            # (Mercurial could cope with that only in cases one of the
            # strings is actually pure ASCII (decoding is trivial)
            logger.error("Encoding of commit message #{message.encoding.name} differs "\
                         "from user name's #{encname}")
          end
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          logger.info("#{logprefix} Actions, done, now committing.")
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          commit_hgsha = hg_commit(share_path, username, message, hg_env, true)
          logger.info("#{logprefix} commit done, changeset is #{commit_hgsha}")

          if topic.nil?
            publish_str, status = popen([hg_exe, 'config', 'experimental.topic.publish-bare-branch'], share_path, hg_env)
            publish = ['yes', 'true', 'on', '1'].include?(publish_str.downcase.strip)
            hg_changeset_publish(user, commit_hgsha) if publish
          end
        ensure
          FileUtils.rm_rf(share_path) unless share_path.nil?
        end
        hg_git_invalidate_maps!
        commit_gitsha = sha_from_hgsha commit_hgsha

        # Same kind of return as gitaly_operation_client.user_commit_files(),
        # itself called from `multi_action()`
        Gitlab::Git::OperationService::BranchUpdate.new(commit_gitsha, repo_creating, branch_creating)
      end

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      # Compute path to a repo namespace HGRC, ready for inclusion from repo's HGRC.
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      # namespace_path: must be relative to the storage root, as @relative_path
      # is.
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      #
      # Returns: path as a string
      def hgrc_inherit_path(namespace_path)
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        Pathname(namespace_path).join('hgrc')
          .relative_path_from(File.join(@hg_relative_path, '.hg')).to_s
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      end

      def hgrc_main_path
        File.join(@hgpath, '.hg', 'hgrc')
      end

      def hgrc_managed
        managed = 'hgrc.managed'
        [managed, File.join(@hgpath, '.hg', managed)]
      end

      HGRC_INCL_INHERIT_RX = /%include .*\/hgrc/.freeze

      # write the repository-local HGRC files.
      #
      # all configuration values are written in a separate `hgrc.managed`
      # file that is completely overwritten.
      #
      # in the main `hgrc`, only inclusions are managed
      #
      # inherit: if true, include directive for the namespace HGRC is included
      #          first if not already there.
      #          if false, it is removed if present
      #          if nil, nothing happens
      # values: two-level Hash, with String leaf values
      #
      # Newlines in values are prohibited (use plain whitespace if needed),
      # as well as in keys (section and item names).
      def set_hgrc(user, inherit, namespace_path, values)
        key_rx = /^\w*$/

        write_main = false
        main_path = hgrc_main_path
        managed, managed_path = hgrc_managed
        incl_managed = "%include " + managed

        main_lines = File.readlines(main_path)
        main_stripped_lines = main_lines.map { |l| l.strip }
        if !main_stripped_lines.include?(incl_managed)
          main_lines.push("\n", incl_managed + "\n")
          write_main = true
        end

        by_line = "by user #{user.username} (id=#{user.id}) at #{Time.new}"
        if inherit.nil?
        elsif inherit
          if match_idx(main_stripped_lines, HGRC_INCL_INHERIT_RX).nil?
            main_lines.insert(0,
                              "%include " + hgrc_inherit_path(namespace_path))
            main_lines.insert(0, "# inheritance restored #{by_line}")
            write_main = true
          end
        else
          inh_idx = match_idx(main_stripped_lines, HGRC_INCL_INHERIT_RX)
          if !inh_idx.nil?
            main_lines[inh_idx] = "# inheritance removed #{by_line}"
            write_main = true
          end
        end

        File.open(managed_path, 'w') do |hgrcf|
          hgrcf.puts(
            "# This file is entirely managed through the GitLab Rails app")
          hgrcf.puts("# last update #{by_line}")

          if !values.nil?
            values.each do |section, items|
              raise InvalidHgSetting(section) unless key_rx.match(section)
              hgrcf.puts("[#{section}]")
              items.each do |item, value|
                raise InvalidHgSetting(item) unless key_rx.match(section)
                raise InvalidHgSetting(value) if value.include?('\n')
                hgrcf.puts("#{item} = #{value}")
              end
              hgrcf.puts()
            end
          end
        end

        if write_main
          File.open(main_path, 'w') do |mainf|
            for line in main_lines
              # note for not-rubyists: puts() adds "\n"  only if needeed
              mainf.puts(line)
            end
          end
        end
      end

      # Read the HGRC configuration files *for this repo*
      #
      # Return a Hash:
      #  'inherit' => bool
      #  'content' => raw content of the managed file
      def get_hgrc
        main_lines = File.readlines(hgrc_main_path)
        main_stripped_lines = main_lines.map { |l| l.strip }
        {
          'inherit' => !match_idx(main_stripped_lines, HGRC_INCL_INHERIT_RX).nil?,
          'content' => File.read(hgrc_managed[1])
        }
      end

      # Check HGRC inheritance from group path and fix it if needed.
      #
      # This is especially useful in cases of repository relocation:
      # - rename
      # - transfer
      # - hashed storage migration
      def check_fix_hgrc_inheritance(namespace_path)
        hgrc_path = hgrc_main_path
        Rails.logger.info("check_fix_hgrc_inheritance called with namespace_path=#{namespace_path} for #{hgrc_path}")
        main_lines = File.readlines(hgrc_path)

        inherit_idx = match_idx(main_lines, HGRC_INCL_INHERIT_RX)
        return if inherit_idx.nil?

        inherit_line = "%include " + hgrc_inherit_path(namespace_path)
        return unless inherit_line != main_lines[inherit_idx].strip

        main_lines[inherit_idx] = inherit_line
        File.open(hgrc_path, 'w') do |mainf|
          for line in main_lines
            # note for not-rubyists: puts() adds "\n"  only if needeed
            mainf.puts(line)
          end
        end
      end

      SAFE_HG_HEPTAPOD_CONFIG = {'allow-multiple-heads' => 'bool',
                                 'allow-bookmarks' => 'bool',
                                 'auto-publish' => 'str'}.freeze
      HG_CONFIG_TRUE = ["1", "yes",  "true", "on"].freeze

      def get_hg_heptapod_config
        hg_env = {'HGUSER' => 'Heptapod system',
                  'HEPTAPOD_SKIP_ALL_GITLAB_HOOKS' => 'yes',
                  'HGRCPATH' => Gitlab::Mercurial.hgrc_path,
                 }
        hg_exe = Gitlab.config.mercurial.bin_path
        out, status = popen([hg_exe, 'config', 'heptapod'],
                            @hgpath, hg_env)
        raise StandardError("Can't read hg repository config") unless status.zero?
        config = {}
        out.lines.each do |line|
          key, value = line.split('=', 2)
          key = key.strip
          next unless key.start_with?('heptapod.')
          key = key[9..]
          # no attempt to convert back, that's up to the user
          # (we'd have to know the type for that)
          value = value.strip
          vtype = SAFE_HG_HEPTAPOD_CONFIG[key]
          next if vtype.nil?  # not a safe item
          config[key] = converted = case vtype
                      when 'bool'
                        HG_CONFIG_TRUE.include?(value)
                      when 'str'
                        value
                      else
                        next
                      end
        end
        config
      end
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    end
  end
end