commit-email.rb: Suppres git signed commit signatures

When setting `log.showSignature=true`, `git log` and `git show`
include messages gpg verfied the commits, in addition to the message
specified by `--pretty`.

Author: nobu

tool/commit-email.rb

@@ -121,7 +121,7 @@ def build_diff(path, numstats)
   end
 
   def git_show(revision, format:)
-    git('show', "--pretty=#{format}", '--no-patch', revision).strip
+    git('show', '--no-show-signature', "--pretty=#{format}", '--no-patch', revision).strip
   end
 
   def git(*args)
@@ -180,7 +180,7 @@ def main(repo_path, to, rest)
     args, options = parse(rest)
 
     infos = args.each_slice(3).flat_map do |oldrev, newrev, refname|
-      revisions = IO.popen(['git', 'log', '--reverse', '--pretty=%H', "#{oldrev}^..#{newrev}"], &:read).lines.map(&:strip)
+      revisions = IO.popen(['git', 'log', '--no-show-signature', '--reverse', '--pretty=%H', "#{oldrev}^..#{newrev}"], &:read).lines.map(&:strip)
       revisions[0..-2].zip(revisions[1..-1]).map do |old, new|
         GitInfoBuilder.new(repo_path).build(old, new, refname)
       end