/usr/share/mercurial/templates/raw/logentry.tmpl is in mercurial-common 3.7.3-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | changeset: {node}
revision: {rev}
user: {author}
date: {date|rfc822date}
summary: {desc}
{branches%branchname}{tags%tagname}{bookmarks%bookmarkname}
|