sync_default_gems.rb: fold too long subject [ci skip]

Line with substituted issue references with URLs are often very long.
Although Git (and GitHub) recommends folding subject lines less than
50 columns, but many commits ignore this, so fold at 68 columns for
now.

tool/sync_default_gems.rb

@@ -422,16 +422,30 @@ def message_filter(repo, sha)
   log = STDIN.read
   log.delete!("\r")
   url = "https://github.com/#{repo}"
-  log.gsub!(/\b(?:(?i:fix(?:e[sd])?) +)\K#(?=\d+\b)|\bGH-#?(?=\d+\b)|\(\K#(?=\d+\))/) {
+  subject, log = log.split("\n\n", 2)
-    "#{url}/pull/"
+  conv = proc do |s|
-  }
+    mod = true if s.gsub!(/\b(?:(?i:fix(?:e[sd])?) +)\K#(?=\d+\b)|\bGH-#?(?=\d+\b)|\(\K#(?=\d+\))/) {
-  log.gsub!(%r{(?<![-\[\](){}\w@/])(?:(\w+(?:-\w+)*/\w+(?:-\w+)*)@)?(\h{10,40})\b}) {|c|
+      "#{url}/pull/"
-    "https://github.com/#{$1 || repo}/commit/#{$2[0,12]}"
+    }
-  }
+    mod |= true if s.gsub!(%r{(?<![-\[\](){}\w@/])(?:(\w+(?:-\w+)*/\w+(?:-\w+)*)@)?(\h{10,40})\b}) {|c|
-  log.sub!(/\s*(?=(?i:\nCo-authored-by:.*)*\Z)/) {
+      "https://github.com/#{$1 || repo}/commit/#{$2[0,12]}"
-    "\n\n" "#{url}/commit/#{sha[0,10]}\n"
+    }
-  }
+    mod
-  print "[#{repo}] ", log
+  end
+  subject = "[#{repo}] #{subject}"
+  subject.gsub!(/\s*\n\s*/, " ")
+  if conv[subject]
+    if subject.size > 68
+      subject.gsub!(/\G.{,67}[^\s.,][.,]*\K\s+/, "\n")
+    end
+  end
+  if log
+    conv[log]
+    log.sub!(/\s*(?=(?i:\nCo-authored-by:.*)*\Z)/) {
+      "\n\n" "#{url}/commit/#{sha[0,10]}\n"
+    }
+  end
+  print subject, "\n\n", log
 end
 
 # NOTE: This method is also used by GitHub ruby/git.ruby-lang.org's bin/update-default-gem.sh