tests: demonstrate how conflict markers end up $local *and* $output
When a merge tool is configured to keep conflict markers, they are
supposed to be written to `$local` if `$output` is not mentioned in
the tool's `merge-tools.<tool>.args` config, and in `$output` if it is
mentioned. However, I broke the latter case in D12190.
Differential Revision: https://phab.mercurial-scm.org/D12378
{
"version": 1,
"project": "mercurial",
"project_url": "https://mercurial-scm.org/",
"repo": "..",
"branches": ["default", "stable"],
"environment_type": "virtualenv",
"show_commit_url": "https://www.mercurial-scm.org/repo/hg/rev/",
"benchmark_dir": "benchmarks",
"env_dir": "../.asv/env",
"results_dir": "../.asv/results",
"html_dir": "../.asv/html"
}