mercurial: pass ui to extensions.load (issue5007) extensions.load does need ui argument to print error if an extension fails to load.

test-patchbomb.t: drop a number of now-redundant uses of "-n"

test-patchbomb.t: test use of sendmail program

merge: add options to warn or ignore on colliding unknown files A 'colliding unknown file' is a file that meets all of the following conditions: - is untracked or ignored on disk - is present in the changeset being merged or updated to - has different contents Previously, we would always abort whenever we saw such files. With this config option we can choose to warn and back the unknown files up instead, or even forgo the warning entirely and silently back the unknown files up. Common use cases for this configuration include a large scale transition of formerly ignored unknown files to tracked files. In some cases the files can be given new names, but in other cases, external "convention over configuration" constraints have determined that the file must retain the same name as before.

batchget: add support for backing up files We're going to use this in an upcoming feature.

merge: add a new 'backup' argument to get actions We're going to use this in an upcoming patch to back untracked files up when they're replaced by tracked ones.

_checkunknownfiles: turn 'conflicts' into a set We'll check for membership in this set in an upcoming patch.

checkunknownfiles: make control flow clearer In particular, make it clear that we only check for and abort on conflicts if force is not true.

_checkunknownfiles: rename 'aborts' to 'conflicts' In upcoming patches we'll be able to do more useful things than aborting.

origpath: move from cmdutil to scmutil This is a lower-level function so it doesn't need to be in cmdutil, and putting it here avoids a bunch of potential import cycle issues.