tests/test-hgrc.out

new extension: fetch -> combine pull and merge/update

pull changes from remote repo.
if changes add new head: merge with new head, commit result.
else: update working dir to new head.

this makes useful command like git 'pull' command.

abort: Failed to parse .../t/.hg/hgrc
File contains no section headers.
file: .../t/.hg/hgrc, line: 1
'invalid\n'