tests/test-merge8.t

tests: conditionalize tests based on presence of revlogs for files

~85 tests don't like our non-revlog file store for various reasons.

This commit introduces hghave functionality for declaring and querying
repository features. By default, we assume repositories have
revlog-based file storage. But if the HGREPOFEATURES environment
variable is set, we can override the default set of repository
features. If you run the test harness with our simplestorerepo
extension and an environment variable set to the proper value, you
can override the hghave defaults to agree with simplestorerepo's
version of reality.

Various tests have been modified so behavior dependent on revlog-based
file storage is marked as such.

This fixes a handful of test failures with our custom file storage
extension. But dozens remain. The point of this commit is to demonstrate
how tests will need to be modified to account for custom storage
implementations.

TBH, I'm not convinced hghave is the proper layer for repository
feature detection. I /think/ we'll eventually want something in
run-tests.py itself. But that would require inventing a new primitive
in the test harness. This is all very alpha at the moment. So I think
hghave is an acceptable place to hang this feature detection. I think
the right time to be thinking about integrating this into run-tests.py
is *after* we have a stable alternate storage implementation in core.
For now, let's try to make progress towards the idea of an alternate
storage backend.

Differential Revision: https://phab.mercurial-scm.org/D3030

Test for changeset ba7c74081861
(update dirstate correctly for non-branchmerge updates)
  $ hg init a
  $ cd a
  $ echo a > a
  $ hg add a
  $ hg commit -m a
  $ cd ..
  $ hg clone a b
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd a
  $ hg mv a b
  $ hg commit -m move
  $ echo b >> b
  $ hg commit -m b
  $ cd ../b
  $ hg pull ../a
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  new changesets e3c9b40284e1:772b37f1ca37
  (run 'hg update' to get a working copy)
  $ hg update
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ cd ..