Martin von Zweigbergk <martinvonz@google.com> [Mon, 14 Dec 2020 18:09:37 -0800] rev 46139
filemerge: add support for the new "mergediff" marker style to premerge
This adds support for the new "mergediff" conflict marker style to
"merge-tools.<tool>.premerge" (the new value is called
"keep-mergediff").
Differential Revision: https://phab.mercurial-scm.org/D9606