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.

logcmdutil: hold makefilematcher/makehunksfilter() by changesetpriner (API) This merges self.matchfn and self.show(matchfn) into self._makefilematcher, and does the same for hunksfilter. Because changesetprinter seems to have too many optional arguments, makefilematcher() and makehunksfilter() will be packed into one object by later patch.

log: pass ctx to makefilematcher() and makehunksfilter() functions This isn't important, but seems more consistent as changesetprinter.show() takes a ctx, not a revision number.

tests: allow age to go up to triple digits in test-shelve.t We started to glob the age of shelved changes in 51934fc796c0, which says that sometimes tests run slow and `hg shelve --list` says "2s" instead of "1s". However in some instances, like [1], tests run so slow that the age goes up to double digits ("13s" in that case). When that happens, `hg shelve --list` output has less white spaces after the age, so let's glob the spaces too. We probably won't ever need to handle triple digits there, but I went ahead and left only 2 required white spaces in total. [1]: https://buildd.debian.org/status/fetch.php?pkg=mercurial&arch=sparc64&ver=4.5-1&stamp=1518360804&raw=0