formatter: add support for changeset templating Some formatter-based commands provide fields that are identical to the ones defined in templatekw, but we had to specify them manually to support all changeset-based template keywords. This patch adds fm.context() that populates all templatekw. These keywords are available only in template output, so we still need to set important keywords via fm.data() if they should be available in e.g. JSON output. Currently fm.context() takes only 'ctx' argument. It will eventually be extended to take 'fctx' to support file-based keywords (e.g. {path}) seen in hgweb.

templatekw: move defaulttmpl constant from changeset_templater These templates are used when rendering inner lists of some template keywords, so it makes sense to define them in templatekw. This allows us to reuse them to create a templateformatter knowing changectx.

formatter: drop filters argument from maketemplater() It's unused now. I want to keep the high-level API simple.

templater: port formatnode filter from changeset_templater This slightly reduces the difference between changeset_templater and formatter, and helps extending formatter to support changeset templating. New formatnode() is not a template filter, but a function since a filter cannot access to ui. And it's marked as DEPRECATED since I think it exists only for compatibility reasons.

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)