Enable even more frozen string in lib/gitlab

Enables frozens string for the following:

* lib/gitlab/conflict/**/*.rb
* lib/gitlab/cross_project_access/**/*.rb
* lib/gitlab/cycle_analytics/**/*.rb
* lib/gitlab/data_builder/**/*.rb
* lib/gitlab/database/**/*.rb
* lib/gitlab/dependency_linker/**/*.rb
* lib/gitlab/diff/**/*.rb
* lib/gitlab/downtime_check/**/*.rb
* lib/gitlab/email/**/*.rb
* lib/gitlab/etag_caching/**/*.rb

Partially addresses gitlab-org/gitlab-ce#47424.

20 files changed, 41 insertions, 1 deletions

diff --git a/lib/gitlab/diff/diff_refs.rb b/lib/gitlab/diff/diff_refs.rb
index 81df47964be..d4823f60826 100644
--- a/lib/gitlab/diff/diff_refs.rb
+++ b/lib/gitlab/diff/diff_refs.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     class DiffRefs
diff --git a/lib/gitlab/diff/file.rb b/lib/gitlab/diff/file.rb
index fb117baca9e..f3bd8b69869 100644
--- a/lib/gitlab/diff/file.rb
+++ b/lib/gitlab/diff/file.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     class File
diff --git a/lib/gitlab/diff/file_collection/base.rb b/lib/gitlab/diff/file_collection/base.rb
index 2ad6fe8449d..10df037a0dd 100644
--- a/lib/gitlab/diff/file_collection/base.rb
+++ b/lib/gitlab/diff/file_collection/base.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     module FileCollection
diff --git a/lib/gitlab/diff/file_collection/commit.rb b/lib/gitlab/diff/file_collection/commit.rb
index 4dc297ec036..7b1d6171e82 100644
--- a/lib/gitlab/diff/file_collection/commit.rb
+++ b/lib/gitlab/diff/file_collection/commit.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     module FileCollection
diff --git a/lib/gitlab/diff/file_collection/compare.rb b/lib/gitlab/diff/file_collection/compare.rb
index 20d8f891cc3..586c5cf87af 100644
--- a/lib/gitlab/diff/file_collection/compare.rb
+++ b/lib/gitlab/diff/file_collection/compare.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     module FileCollection
diff --git a/lib/gitlab/diff/file_collection/merge_request_diff.rb b/lib/gitlab/diff/file_collection/merge_request_diff.rb
index 0dd073a3a8e..e29bf75f341 100644
--- a/lib/gitlab/diff/file_collection/merge_request_diff.rb
+++ b/lib/gitlab/diff/file_collection/merge_request_diff.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     module FileCollection
diff --git a/lib/gitlab/diff/formatters/base_formatter.rb b/lib/gitlab/diff/formatters/base_formatter.rb
index 5e923b9e602..9704aed82c1 100644
--- a/lib/gitlab/diff/formatters/base_formatter.rb
+++ b/lib/gitlab/diff/formatters/base_formatter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     module Formatters
diff --git a/lib/gitlab/diff/formatters/image_formatter.rb b/lib/gitlab/diff/formatters/image_formatter.rb
index ccd0d309972..5bc9f0c337f 100644
--- a/lib/gitlab/diff/formatters/image_formatter.rb
+++ b/lib/gitlab/diff/formatters/image_formatter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     module Formatters
diff --git a/lib/gitlab/diff/formatters/text_formatter.rb b/lib/gitlab/diff/formatters/text_formatter.rb
index 01c7e9f51ab..f6e247ef665 100644
--- a/lib/gitlab/diff/formatters/text_formatter.rb
+++ b/lib/gitlab/diff/formatters/text_formatter.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     module Formatters
diff --git a/lib/gitlab/diff/highlight.rb b/lib/gitlab/diff/highlight.rb
index 1d833183ec3..d2484217ab9 100644
--- a/lib/gitlab/diff/highlight.rb
+++ b/lib/gitlab/diff/highlight.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     class Highlight
diff --git a/lib/gitlab/diff/image_point.rb b/lib/gitlab/diff/image_point.rb
index 1f157354ea4..a3ce032f8e2 100644
--- a/lib/gitlab/diff/image_point.rb
+++ b/lib/gitlab/diff/image_point.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     class ImagePoint
diff --git a/lib/gitlab/diff/inline_diff.rb b/lib/gitlab/diff/inline_diff.rb
index 72d5ec547da..5815d1bae4a 100644
--- a/lib/gitlab/diff/inline_diff.rb
+++ b/lib/gitlab/diff/inline_diff.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     class InlineDiff
@@ -71,7 +73,7 @@ module Gitlab
         def find_changed_line_pairs(lines)
           # Prefixes of all diff lines, indicating their types
           # For example: `" - +  -+  ---+++ --+  -++"`
-          line_prefixes = lines.each_with_object("") { |line, s| s << (line[0] || ' ') }.gsub(/[^ +-]/, ' ')
+          line_prefixes = lines.each_with_object(+"") { |line, s| s << (line[0] || ' ') }.gsub(/[^ +-]/, ' ')
 
           changed_line_pairs = []
           line_prefixes.scan(LINE_PAIRS_PATTERN) do
diff --git a/lib/gitlab/diff/inline_diff_markdown_marker.rb b/lib/gitlab/diff/inline_diff_markdown_marker.rb
index c2a2eb15931..3c536c43a9e 100644
--- a/lib/gitlab/diff/inline_diff_markdown_marker.rb
+++ b/lib/gitlab/diff/inline_diff_markdown_marker.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     class InlineDiffMarkdownMarker < Gitlab::StringRangeMarker
diff --git a/lib/gitlab/diff/inline_diff_marker.rb b/lib/gitlab/diff/inline_diff_marker.rb
index 81e91ea0ab7..1bbde1ffd2a 100644
--- a/lib/gitlab/diff/inline_diff_marker.rb
+++ b/lib/gitlab/diff/inline_diff_marker.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     class InlineDiffMarker < Gitlab::StringRangeMarker
diff --git a/lib/gitlab/diff/line.rb b/lib/gitlab/diff/line.rb
index 5b67cd46c48..74fed7c4b1b 100644
--- a/lib/gitlab/diff/line.rb
+++ b/lib/gitlab/diff/line.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     class Line
diff --git a/lib/gitlab/diff/line_mapper.rb b/lib/gitlab/diff/line_mapper.rb
index cf71d47df8e..fba7bff4781 100644
--- a/lib/gitlab/diff/line_mapper.rb
+++ b/lib/gitlab/diff/line_mapper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # When provided a diff for a specific file, maps old line numbers to new line
 # numbers and back, to find out where a specific line in a file was moved by the
 # changes.
diff --git a/lib/gitlab/diff/parallel_diff.rb b/lib/gitlab/diff/parallel_diff.rb
index 0cb26fa45c8..77b65fea726 100644
--- a/lib/gitlab/diff/parallel_diff.rb
+++ b/lib/gitlab/diff/parallel_diff.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     class ParallelDiff
diff --git a/lib/gitlab/diff/parser.rb b/lib/gitlab/diff/parser.rb
index 7ae7ed286ed..4a47e4b80b6 100644
--- a/lib/gitlab/diff/parser.rb
+++ b/lib/gitlab/diff/parser.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module Gitlab
   module Diff
     class Parser
diff --git a/lib/gitlab/diff/position.rb b/lib/gitlab/diff/position.rb
index f967494199e..9c4d9377593 100644
--- a/lib/gitlab/diff/position.rb
+++ b/lib/gitlab/diff/position.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Defines a specific location, identified by paths line numbers and image coordinates,
 # within a specific diff, identified by start, head and base commit ids.
 module Gitlab
diff --git a/lib/gitlab/diff/position_tracer.rb b/lib/gitlab/diff/position_tracer.rb
index 8457e0c4cb6..af3df820422 100644
--- a/lib/gitlab/diff/position_tracer.rb
+++ b/lib/gitlab/diff/position_tracer.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 # Finds the diff position in the new diff that corresponds to the same location
 # specified by the provided position in the old diff.
 module Gitlab