devise

https://github.com/plataformatec/devise

Ruby

Flexible authentication solution for Rails with Warden.

Mail::Header#fields=

3.6. Field definitions
 
  It is important to note that the header fields are not guaranteed to
  be in a particular order.  They may appear in any order, and they
  have been known to be reordered occasionally when transported over
  the Internet.  However, for the purposes of this standard, header
  fields SHOULD NOT be reordered when a message is transported or
  transformed.  More importantly, the trace header fields and resent
  header fields MUST NOT be reordered, and SHOULD be kept in blocks
  prepended to the message.  See sections 3.6.6 and 3.6.7 for more
  information.

Populates the fields container with Field objects in the order it
receives them in.

Acceps an array of field string values, for example:

 h = Header.new
 h.fields = ['From: [email protected]', 'To: [email protected]']

Source | Google | Stack overflow

Edit

git clone [email protected]:plataformatec/devise.git
cd devise
open

Contribute

# Make a new branch

git checkout -b -your-name--update-docs-Mail--Header-fields--for-pr

# Commit to git

git add git commit -m "better docs for Mail::Header#fields="

# Open pull request

gem install hub # on a mac you can `brew install hub`

hub fork

git push <your name> -your-name--update-docs-Mail--Header-fields--for-pr

hub pull-request

# Celebrate!