Refactor how Mercurial runs commands that require extensions
ac365c3ee509
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Description

Refactor how Mercurial runs commands that require extensions

Summary:
Currently there are a number of --config extensions.blah= sprinkled throughout the Mercurial APIs which aren't pleasant to look at. Additionally it turns out the rebase command requires the rebase extension which is not turned on by default. Uses of rebase should also be including this flag to enable the extension when it's in use.

This adds ArcanistMercurialAPI::buildMercurialExtensionCommand() which allows running a Mercurial command that requires an extension just by naming the extension instead of providing the full --config.. argument.

It can be used e.g.

$api->execxLocalWithExtension(
  'strip',
  'strip --rev %s --',
  $rev);

$api->execxLocalWithExtension(
  'arc-hg',
  'arc-amend --logfile %s',
  $tmp_file);

Which produces

$ hg --encoding utf-8 --config 'extensions.strip=' strip --rev 82567759e2d703e1e0497f5f41363de3a1500188 --

$ hg --encoding utf-8 --config 'extensions.arg-hg=/Users/cspeckrun/Source/phacility/arcanist/support/hg/arc-hg.py' arc-amend --logfile /private/var/folders/cg/364w44254v5767ydf_x1tg_80000gn/T/6bwck66ccx0kwskw/89989-5F8JaL

Refs T13659

Test Plan: I ran through several scenarios of running arc diff and arc land with uncommitted changes on non-head commits, while not having the evolve extension enabled. Using the --trace argument I verified that rebase, strip, arc-amend, and arc-ls-markers were all invoked and the corresponding arc diff and arc land commands succeeded. I also ran arc land --onto-remote default while arc-hg.py raised an exception for the "remote" case and verified that the error was caught by Arcanist and displayed the error and prevented further execution. I removed the error from arc-hg.py and re-ran the command and verified it succeeded.