tests/test-merge4.t

rhg: Port Python’s `ui.configlist` as `Config::get_list`

This new method is not used yet outside of its own unit tests,
so this changeset should make no observable change.

The Rust parser implementation attempts to exactly replicate the behavior of
the Python one, even in edge cases where that behavior is… surprising.
New unit tests capture some of these edge cases.

This started as a line-by-line port. The main changes are:

* Pass around a parser mode enum instead of parser functions
* Inline the whole parser into one function
* Use `[u8]::get` which returns an `Option`,
  instead of indexing  after explicitly checking the length.

Differential Revision: https://phab.mercurial-scm.org/D11389

  $ hg init
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ echo This is file b1 > b
  $ hg add b
  $ hg commit -m "commit #1"
  $ hg update 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo This is file c1 > c
  $ hg add c
  $ hg commit -m "commit #2"
  created new head
  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ rm b
  $ echo This is file c22 > c

Test hg behaves when committing with a missing file added by a merge

  $ hg commit -m "commit #3"
  abort: cannot commit merge with missing files
  [255]


Test conflict*() revsets

# Bad usage
  $ hg log -r 'conflictlocal(foo)'
  hg: parse error: conflictlocal takes no arguments
  [10]
  $ hg log -r 'conflictother(foo)'
  hg: parse error: conflictother takes no arguments
  [10]
  $ hg co -C .
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
# No merge parents when not merging
  $ hg log -r 'conflictlocal() + conflictother()'
# No merge parents when there is no conflict
  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg log -r 'conflictlocal() + conflictother()'
  $ hg co -C .
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo conflict > b
  $ hg ci -Aqm 'conflicting change to b'
  $ hg merge 1
  merging b
  warning: conflicts while merging b! (edit, then use 'hg resolve --mark')
  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges or 'hg merge --abort' to abandon
  [1]
# Shows merge parents when there is a conflict
  $ hg log -r 'conflictlocal()' -T '{rev} {desc}\n'
  3 conflicting change to b
  $ hg log -r 'conflictother()' -T '{rev} {desc}\n'
  1 commit #1