Incorrectly decodes subject that is encoded in UTF-8

[niandy]

I use mail 2.5.4 with redmine and I found out that Encodings.value_decode() in encodings.rb sometimes returns incorrect values for subject when it is encoded in UTF-8. It happens when the subject contains 2 strings like this
=?UTF-8?B?0J/RgNC+0YjRgyDRgNCw0LfQvtCx0YDQsNGC0YzRgdGPINC4IA==?=
=?UTF-8?B?0L/RgNC40L3Rj9GC0Ywg0YHRgNC+0YfQvdGL0LUg0LzQtdGA0YssINCyIA==?=

When value_decode calls collapse_adjacent_encodings it will turn the strings into
one
=?UTF-8?B?0J/RgNC+0YjRgyDRgNCw0LfQvtCx0YDQsNGC0YzRgdGPINC4IA==
0L/RgNC40L3Rj9GC0Ywg0YHRgNC+0YfQvdGL0LUg0LzQtdGA0YssINCyIA==?=

However str.unpack('m') will only decode the first of initial strings. I mean that

puts 
"0J/RgNC+0YjRgyDRgNCw0LfQvtCx0YDQsNGC0YzRgdGPINC4IA==".unpack('m').first.force_encoding('utf-8')

and

puts "0J/RgNC+0YjRgyDRgNCw0LfQvtCx0YDQsNGC0YzRgdGPINC4IA==0L/RgNC40L3Rj9GC0Ywg0YHRgNC+0YfQvdGL0LUg0LzQtdGA0YssINCyIA==".unpack('m').first.force_encoding('utf-8')

will return the same result. I believe it's because the decode from base64 function will always stop when it gets '=' or '==' symbols in base64 string. So, I think, collapsing adjacent encodings is not a proper thing to do at all. Cause you still have to decode every string separately.

[jeremy]

Fixed on master.

[eileencodes]

In case anyone is curious the commit that fixed this was b832faf