tests/test-imports-checker.t

phases: invalidate the phases set less often on retract boundary

We already have the information to update the phase set, so we do so directly
instead of invalidating the cache.

This show a sizeable speedup in our `perf::unbundle` benchmark on the
many-draft mozilla-try repository.

### data-env-vars.name            = mozilla-try-2023-03-22-zstd-sparse-revlog
  # benchmark.name                = hg.perf.perf-unbundle
  # bin-env-vars.hg.flavor        = no-rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.issue6528  = disabled

  # benchmark.variants.revs = last-10
before: 2.055259 seconds
after:  1.887064 seconds (-8.18%)
  # benchmark.variants.revs = last-100
before: 2.409239 seconds
after:  2.222429 seconds (-7.75%)
  # benchmark.variants.revs = last-1000
before: 3.945648 seconds
after:  3.762480 seconds (-4.64%)

#require test-repo

  $ . "$TESTDIR/helpers-testrepo.sh"
  $ testrepohgenv
  $ import_checker="$TESTDIR"/../contrib/import-checker.py

Run the doctests from the import checker, and make sure
it's working correctly.
  $ TERM=dumb
  $ export TERM
  $ "$PYTHON" -m doctest $import_checker

Run additional tests for the import checker

  $ mkdir testpackage
  $ touch testpackage/__init__.py

  $ cat > testpackage/multiple.py << EOF
  > import os, sys
  > EOF

  $ cat > testpackage/unsorted.py << EOF
  > import sys
  > import os
  > EOF

  $ cat > testpackage/stdafterlocal.py << EOF
  > from . import unsorted
  > import os
  > EOF

  $ cat > testpackage/requirerelative.py << EOF
  > import testpackage.unsorted
  > EOF

  $ cat > testpackage/importalias.py << EOF
  > import ui
  > EOF

  $ cat > testpackage/relativestdlib.py << EOF
  > from .. import os
  > EOF

  $ cat > testpackage/stdlibfrom.py << EOF
  > from collections import abc
  > EOF

  $ cat > testpackage/symbolimport.py << EOF
  > from .unsorted import foo
  > EOF

  $ cat > testpackage/latesymbolimport.py << EOF
  > from . import unsorted
  > from mercurial.node import hex
  > EOF

  $ cat > testpackage/multiplegroups.py << EOF
  > from . import unsorted
  > from . import more
  > EOF

  $ mkdir testpackage/subpackage
  $ cat > testpackage/subpackage/levelpriority.py << EOF
  > from . import foo
  > from .. import parent
  > EOF

  $ touch testpackage/subpackage/foo.py
  $ cat > testpackage/subpackage/__init__.py << EOF
  > from . import levelpriority  # should not cause cycle
  > EOF

  $ cat > testpackage/subpackage/localimport.py << EOF
  > from . import foo
  > def bar():
  >     # should not cause "higher-level import should come first"
  >     from .. import unsorted
  >     # but other errors should be detected
  >     from .. import more
  >     import testpackage.subpackage.levelpriority
  > EOF

  $ cat > testpackage/importmodulefromsub.py << EOF
  > from .subpackage import foo  # not a "direct symbol import"
  > EOF

  $ cat > testpackage/importsymbolfromsub.py << EOF
  > from .subpackage import foo, nonmodule
  > EOF

  $ cat > testpackage/sortedentries.py << EOF
  > from . import (
  >     foo,
  >     bar,
  > )
  > EOF

  $ cat > testpackage/importfromalias.py << EOF
  > from . import ui
  > EOF

  $ cat > testpackage/importfromrelative.py << EOF
  > from testpackage.unsorted import foo
  > EOF

  $ mkdir testpackage2
  $ touch testpackage2/__init__.py

  $ cat > testpackage2/latesymbolimport.py << EOF
  > from testpackage import unsorted
  > from mercurial.node import hex
  > EOF

# Shadowing a stdlib module to test "relative import of stdlib module" is
# allowed if the module is also being checked

  $ mkdir email
  $ touch email/__init__.py
  $ touch email/errors.py
  $ cat > email/utils.py << EOF
  > from . import errors
  > EOF

  $ "$PYTHON" "$import_checker" testpackage*/*.py testpackage/subpackage/*.py \
  >   email/*.py
  testpackage/importalias.py:1: ui module must be "as" aliased to uimod
  testpackage/importfromalias.py:1: ui from testpackage must be "as" aliased to uimod
  testpackage/importfromrelative.py:1: import should be relative: testpackage.unsorted
  testpackage/importfromrelative.py:1: direct symbol import foo from testpackage.unsorted
  testpackage/importsymbolfromsub.py:1: direct symbol import nonmodule from testpackage.subpackage
  testpackage/latesymbolimport.py:2: symbol import follows non-symbol import: mercurial.node
  testpackage/multiple.py:1: multiple imported names: os, sys
  testpackage/multiplegroups.py:2: multiple "from . import" statements
  testpackage/relativestdlib.py:1: relative import of stdlib module
  testpackage/requirerelative.py:1: import should be relative: testpackage.unsorted
  testpackage/sortedentries.py:1: imports from testpackage not lexically sorted: bar < foo
  testpackage/stdafterlocal.py:2: stdlib import "os" follows local import: testpackage
  testpackage/stdlibfrom.py:1: direct symbol import abc from collections
  testpackage/subpackage/levelpriority.py:2: higher-level import should come first: testpackage
  testpackage/subpackage/localimport.py:6: multiple "from .. import" statements
  testpackage/subpackage/localimport.py:7: import should be relative: testpackage.subpackage.levelpriority
  testpackage/symbolimport.py:1: direct symbol import foo from testpackage.unsorted
  testpackage/unsorted.py:2: imports not lexically sorted: os < sys
  testpackage2/latesymbolimport.py:2: symbol import follows non-symbol import: mercurial.node
  [1]