Turns out it didn't fix test failures like I thought. It only added
more!

This reverts commit b8221c6b.

Both v1 and v2 of the AWS Ruby SDK accept the string literal AES256, no need to differentiate. (thank you, @trevorrowe)

Further changes to Paperclip::Storage::S3 for choosing aws-sdk-v2 before aws-sdk-v1; use object.upload_file rather than object.put; implement v2 expiring_url method

According to the ImageMagick documentation the '@' flag is a special case that
can be used in conjunction with '>' to prevent IM from scaling an image up.
The '<' flag is ignored when using '@'.

http://www.imagemagick.org/Usage/resize/#pixel

This fixes the issue I reported in #1851

It should never be the case that `url` returns `nil`. If there is no url
that can be reasonable achieved, as is the case when the record the
attachment is attached to is unpersisted, then `url` should return the
default url.

[ci skip]

[ci skip]

For the full details of what is included in this release, check out NEWS.

[fixes #1875]

Thanks to MORI Shingo of DeNA Co., Ltd. for reporting this.

There is an issue where if an HTML file is uploaded with a .html
extension, but the content type is listed as being `image/jpeg`, this
will bypass a validation checking for images. But it will also pass the
spoof check, because a file named .html and containing actual HTML
passes the spoof check.

This change makes it so that we also check the supplied content type. So
even if the file contains HTML and ends with .html, it doesn't match the
content type of `image/jpeg` and so it fails.

Mime-types 2.6.1+ has a columnar store that only loads the data that is
needed for a drastically reduced memory footprint.
cc/ @jeremyevans @halostatue

See: https://github.com/mime-types/ruby-mime-types/pull/96.

[fixes #1873]

consistent with public URLs, this also changes the default behavior
for expiring URLs to use the https scheme rather than http.

[closes #1655]

Normally, all of the settings would be set on `Attachment`, and they
were `deep_merge`d fine. However, if you set the global

    config.paperclip_defaults = { :validate_media_type => false }

then the `HasAttachedFile` class wouldn't pick up on it, because it only
uses things that are defined in the class. This change makes it so that
the default options are merged in to the ones that `HasAttachedFile`
uses when it sets up the attachment.

Fixes #1857

Present methods in roughly the same order as they are referenced,
to make it more graceful to read without jumping back and forth.

In other parts of the codebase, "filename" refers to the part after the
directory path it is contained in. e.g. `original_filename` in
attachment.rb.

This makes this file easier to read by conveying the range of arguments
ContentTypeDetector.new accepts.

Prioritize MimeMagic over the `file` binary for content type detection
when it finds a match. Fall back to `file` if MimeMagic can't match
anything.

`file` incorrectly detects Open Office XML files (e.g., xlsx, docx) as
zip since they're implemented as zipped archives of xml files. MimeMagic
detects them properly.

The `aws-sdk` development dependency was updated to `~> 1.6` in #1816
to resolve issues with the creation of 0-byte files on S3 (see #1729).
However, there is no runtime dependency on `aws-sdk`, and the
documentation still suggests that users install an earlier version of
`aws-sdk` that produces the problems in the referenced issue.

This commit updates the docs to recommend the use of `aws-sdk` `~> 1.6`
with Paperclip.

* Uses Paperclip's Tempfile instead of Ruby's in Thumbnail
* Also includes a test for TempfileFactory to be sure it does not revert to similar behavior
* In the tests, give the OS some wiggle room in the Tempfile name to ensure the error does not occur before we are ready for it. The wiggle room is needed because the randomized part of the name has a variable number of characters.

Rescue only `NotIdentifiedByImageMagickError` in
`Attachment#post_process_style`. Other errors should bubble up, because
they are meaningless for the end-user, but important for the programmer.

Fixes #1352.

It's useless because there is the same conditional in https://github.com/thoughtbot/paperclip/blob/master/lib/paperclip/railtie.rb#L25, and if ActiveRecord is not defined, Glue will not run.

The reason behind this I'm trying to use StringioAdapter inside the mailer, and it fails because `length` used in one of the `mail` gem:
https://github.com/mikel/mail/blob/master/lib/mail/message.rb#L1997

Also you can see that normally `size` has `length` alias, for example in a `StringIO` class:
http://ruby-doc.org/stdlib-1.9.3/libdoc/stringio/rdoc/StringIO.html#method-i-length

Let me know, if this change requires test case, I will add it.

As referenced in #1739

Just because the `Rails` constant is defined, it doesn't mean we're
actually in a Rails app. Since there are people who use Paperclip
outside of Rails, and there's no reason we shouldn't be able to run in
those situations. This commit checks for `Rails.env` instead of just
checking for `Rails` and assuming `Rails.env` works.

This reverts commit 06802254.

@see https://github.com/thoughtbot/paperclip/commit/804b4edc1d8d7ca9865170e34f26da7d66f6d0d5#commitcomment-8497017

Including + now.