Compact the git commit message template

[emaste]

Summary

git's default commit message includes the list of staged, unstaged, and untracked files; adding our metadata tags and their descriptions makes for a very long template.

Move the descriptions on to the metadata lines themselves.

[emaste]

In use it would look something like

prepare-commit-msg: compact the template

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
#                                                         72 columns --|
#
# Uncomment and complete these metadata fields, as appropriate:
#
# PR:           <If and which Problem Report is related.>
# Submitted by: <If someone else sent in the change.>
# Reported by:  <If someone else reported the issue.>
# Reviewed by:  <If someone else reviewed your modification.>
# Approved by:  <If you needed approval for this commit.>
# Obtained from:        <If the change is from a third party.>
# MFC after:    <N [day[s]|week[s]|month[s]].  Request a reminder email>
# MFH:          <Ports tree branch name.  Request approval for merge.>
# Relnotes:     <Set to 'yes' for mention in release notes.>
# Security:     <Vulnerability reference (one per line) or description.>
Sponsored by:   The FreeBSD Foundation
# Pull Request: <https://github.com/freebsd/<repo>/pull/###>
# Differential Revision:        <https://reviews.freebsd.org/D###>
#
# "Pull Request" and "Differential Revision" require the *full* GitHub or
# Phabricator URL.
#
# Date:      Thu Dec 17 19:52:30 2020 -0500
#
# On branch wipbsd.20201216
# Changes to be committed:
#       modified:   tools/tools/git/hooks/prepare-commit-msg
#
# Untracked files:
#       ItaniumDemangle.o

[bcr]

It looks good to me, wording and all.

[emaste]

Committed as a62107ed19a1095158f454132a3b6ec536a4de7c