Some MTAs insert newlines into email content to limit line length to
around 1000 characters. Because the HTML part of Gerrit emails used HTML
breaks for line wrapping, lines in the raw message would easily exceed
1000 characters. At best, the newline would be inserted amid text,
resulting on odd prose or an incorrect code quote. At worst, the newline
would appear in HTML code, resulting in an invalid tree.
With this change, the text and HTML parts of emails sent through SMTP
are converted to the quoted-printable content-transfer-encoding. In this
way, lines are limited to 76 characters via "soft breaks".
With this encoding, the raw email content will only contain 7-bit ASCII
characters, which avoids other potential issues with older MTAs.
Bug: Issue 6527
Change-Id: I9adc5b4d69f4bd3f2bc580ff62de1e8b0f4ebbb6
da65bcc156