merge: cut import cycle at merge -> extensions This seems less bad because checking fsmonitor looks like a temporary hack, and cmdutil -> mergemod should be a valid dependency.

subrepo: split non-core functions to new module Resolves import cycle caused by subrepo -> cmdutil. Still we have another cycle, cmdutil -> context -> subrepo, but where I think importing context is wrong. Perhaps we'll need repo.makememctx().

diff: remove fp.write() wrapper which drops label argument It's no longer needed since we've split labeled write() from file-like write().

log: pack filematcher and hunksfilter into changesetdiffer object This is just a way of getting rid of clumsy makefilematcher/makehunksfilter arguments. There might be a better abstraction, but I don't think this is bad. This makes filematcher and hunksfilter available by default, but that should be fine.

log: drop dead code to concatenate --line-range patterns and pats It's disabled since 2e45bbd3db7b, and the current implementation is unlikely to be reused.

logcmdutil: create hunksfilter and filematcher even if no diff option given It's okay since 5fe6f946f111, "log: allow matchfn to be non-null even if both --patch/--stat are off."

logcmdutil: unindent diff generator of changesetprinter Prepares for the next few patches which will make matchfn and hunksfilterfn always available.