Consider following LDAP search query example:

    (&(objectClass=Person)(|(uid=%s)(mail=%s)))

Right now on first login attempt Gogs will use the text supplied on login form
as the newly created user name. In example query above the text matches against
both e-mail or user name. So if user puts the e-mail then the new Gogs user
name will be e-mail which may be undesired.

Using optional user name attribute setting we can explicitly say we want Gogs
user name to be certain LDAP attribute eg. `uid`, so even user will use e-mail
to login 1st time, the new account will receive correct user name.

The hyperlink and the display name of the branch if the branch is in a folder or the branch name has '#'

- copy link button: #1396, #1168, #1668,
- synxtax highlight: #1712, #1549, #1315, #670
- z-index: #1942

"Enable this to disable..." is needlessly confusing, simplify it by being
upfront that this setting disables the Gravatar fetching.

- #1496: fallback plain text
- #1002: add date header
- #913: fix encoding of header