tests/failfilemerge.py

nodemap: introduce append-only incremental update of the persistent data

Rewriting the full nodemap for each transaction has a cost we would like to
avoid. We introduce a new way to write persistent nodemap data by adding new
information at the end for file. Any new and updated block as added at the end
of the file. The last block is the new root node.

With this method, some of the block already on disk get "dereferenced" and
become dead data. In later changesets, We'll start tracking the amount of dead
data to eventually re-generate a full nodemap.

Differential Revision: https://phab.mercurial-scm.org/D7886

# extension to emulate interrupting filemerge._filemerge

from __future__ import absolute_import

from mercurial import (
    error,
    extensions,
    filemerge,
)


def failfilemerge(
    filemergefn, premerge, repo, wctx, mynode, orig, fcd, fco, fca, labels=None
):
    raise error.Abort("^C")
    return filemergefn(premerge, repo, mynode, orig, fcd, fco, fca, labels)


def extsetup(ui):
    extensions.wrapfunction(filemerge, '_filemerge', failfilemerge)