Improved large commit handling.

Previously, only number of changed files mattered. Now, number of lines to render in the diff are also taken into account.

A hard limit is set, above which diffs are not rendered and users are not allowed to override that. This prevents high server
resource usage with huge commits.

Related to #1745, #2259

In addition, handle large commits for MergeRequests and Compare controllers.

Also fixes a bug where diffs are loaded twice, if user goes directly to merge_requests/:id/diffs URL.

1 files changed, 41 insertions, 2 deletions

diff --git a/app/models/commit.rb b/app/models/commit.rb
index f8ca6a5fe82..dd1f9801878 100644
--- a/app/models/commit.rb
+++ b/app/models/commit.rb
@@ -6,15 +6,41 @@ class Commit
 
   attr_mentionable :safe_message
 
-  # Safe amount of files with diffs in one commit to render
+  # Safe amount of changes (files and lines) in one commit to render
   # Used to prevent 500 error on huge commits by suppressing diff
   #
-  DIFF_SAFE_SIZE = 100
+  # User can force display of diff above this size
+  DIFF_SAFE_FILES  = 100
+  DIFF_SAFE_LINES  = 5000
+  # Commits above this size will not be rendered in HTML
+  DIFF_HARD_LIMIT_FILES = 500
+  DIFF_HARD_LIMIT_LINES = 10000
 
   def self.decorate(commits)
     commits.map { |c| self.new(c) }
   end
 
+  # Calculate number of lines to render for diffs
+  def self.diff_line_count(diffs)
+    diffs.reduce(0){|sum, d| sum + d.diff.lines.count}
+  end
+
+  def self.diff_suppress?(diffs, line_count = nil)
+    # optimize - check file count first
+    return true if diffs.size > DIFF_SAFE_FILES
+
+    line_count ||= Commit::diff_line_count(diffs)
+    line_count > DIFF_SAFE_LINES
+  end
+
+  def self.diff_force_suppress?(diffs, line_count = nil)
+    # optimize - check file count first
+    return true if diffs.size > DIFF_HARD_LIMIT_FILES
+
+    line_count ||= Commit::diff_line_count(diffs)
+    line_count > DIFF_HARD_LIMIT_LINES
+  end
+
   attr_accessor :raw
 
   def initialize(raw_commit)
@@ -27,6 +53,19 @@ class Commit
     @raw.id
   end
 
+  def diff_line_count
+    @diff_line_count ||= Commit::diff_line_count(self.diffs)
+    @diff_line_count
+  end
+
+  def diff_suppress?
+    Commit::diff_suppress?(self.diffs, diff_line_count)
+  end
+
+  def diff_force_suppress?
+    Commit::diff_force_suppress?(self.diffs, diff_line_count)
+  end
+
   # Returns a string describing the commit for use in a link title
   #
   # Example