Making the width of the phriction preview match the width of the actual content

Summary: Making the width of the phriction preview match the width of the actual content

Test Plan: Edit a phriction article and see that the preview is the correct size

Reviewers: chad, #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5243

Differential Revision: https://secure.phabricator.com/D9351
Fix undefinded $changesets when submitting inline comments in Differential

Summary: Fixes T5262. This branch is overzealous, and causes us to fail to load changeses if `metamta.differential.unified-comment-context` is off. It was on for me locally for testing, which is why I missed this.

Test Plan: No more exception.

Reviewers: chad

Reviewed By: chad

Subscribers: richardvanvelzen, epriestley

Maniphest Tasks: T5262

Differential Revision: https://secure.phabricator.com/D9376
Merge branch 'master-upstream'
HTML emails + basic DIFF colorizing

Summary:
Added support for side-by-side HTML and plaintext email building.
Also generate slightly colorized diff content in emails.

This is enabled by a new config, metamta.html-emails

Test Plan: Tested locally, but needs some unit tests probably.

Reviewers: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9375
Merge branch 'html_emails'