Major changes

The compiler team uses the major change process, which requires:

• An issue
• A second

We have supporting automation for both parts.

First, on the rust-lang/compiler-team repository, an issue with the major-change label is created via the template. Once that's opened, it automatically gains the "to-announce" label which should be removed when it's announced at a compiler team meeting.

For seconds, you tell rustbot @rustbot seconded or @rustbot second and it will apply the relevant label. Only team members can do so.

Configuration:

[major-change]
# This is the label to be added to newly opened proposals, so they can 
# be discussed in a meeting.
meeting_label = "to-announce"

# This is the label applied when issuing a `@rustbot second` command, it
# indicates that the proposal has moved into the 10 day waiting period.
second_label = "final-comment-period"

# Extra text that is added to the comment posted to the proposal issue.
open_extra_text = "cc @rust-lang/compiler @rust-lang/compiler-contributors"

# The stream where the major change will be announced.
# can be found by looking for the first number in URLs, e.g. https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler
zulip_stream = 233931

# A username (typically a group, e.g. T-lang) to ping on Zulip for newly
# opened proposals.
zulip_ping = "T-compiler"

# This label allows an issue to participate in the major change process
# (i.e., creates a Zulip thread, tracks seconding, etc.).
# The default is `major-change` if not specified (for backwards compatibility).
enabling_label = "major-change"

# This is the label applied after the waiting period has successfully
# elapsed (currently not automatically applied; this must be done
# manually).
# The default is `major-change-accepted` if not spcified (for backwards compatibility).
accept_label = "major-change-accepted"