update: allow setting default update check to "noconflict"
The new value allows update (linear or not) as long as they don't
result in file merges.
I'm hoping that this value can some day become the default.
update: add experimental config for default way of handling dirty wdir
This allows the user to set e.g. experimental.updatecheck=abort to
abort update if the working directory is dirty, but still be able to
override the behavior with e.g. --merge when needed.
I considered adding a --mergelinear option to get back the old
behavior even when experimental.updatecheck=abort is set, but I
couldn't see why anyone would prefer that over --merge.
The default is read in hg.updatetotally(), which means it also applies
to "hg pull -u" and "hg unbundle -u".
update: accept --merge to allow merging across topo branches (
issue5125)
merge: clarify non-linear default updates in docstring table
Non-linear updates won't happen by default, regardless of -c/-C.