tests/failfilemerge.py

log: resolve --follow thoroughly in getlogrevs()

This makes sense because --follow isn't really an option to filter revisions,
but an option to extend revisions to be filtered.

_fileancestors() is a minimal copy of revset._follow(). They are slightly
different in that which revision the matcher sees. _fileancestors() also
uses ctx.walk() instead of ctx.manifest().walk() to show a better warning
on bad match, which will be tested later.

# 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)