import-checker: make imported_modules yield absolute dotted_name_of_path
This patch makes `imported_modules()` always yield absolute
`dotted_name_of_path()`-ed name by strict detection with
`fromlocal()`.
This change improves circular detection in some points:
- locally defined modules, of which name collides against one of
standard library, can be examined correctly
For example, circular import related to `commands` is overlooked
before this patch.
- names not useful for circular detection are ignored
Names below are also yielded before this patch:
- module names of standard library (= not locally defined one)
- non-module names (e.g. `node.nullid` of `from node import nullid`)
These redundant names decrease performance of circular detection.
For example, with files at
1ef96a3b8b89, average loops per file in
`checkmod()` is reduced from 165 to 109.
- `__init__` can be handled correctly in `checkmod()`
For example, current implementation has problems below:
- `from xxx import yyy` doesn't recognize `xxx.__init__` as imported
- `xxx.__init__` imported via `import xxx` is treated as `xxx`,
and circular detection is aborted, because `key` of such
module name is not `xxx` but `xxx.__init__`
- it is easy to enhance for `from . import xxx` style or so (in the
future)
Module name detection in `imported_modules()` can use information
in `ast.ImportFrom` fully.
It is assumed that all locally defined modules are correctly specified
to `import-checker.py` at once.
Strictly speaking, when `from foo.bar.baz import module1` imports
`foo.bar.baz.module1` module, current `imported_modules()` yields only
`foo.bar.baz.__init__`, even though also `foo.__init__` and
`foo.bar.__init__` should be yielded to detect circular import
exactly.
But this limitation is reasonable one for improvement in this patch,
because current `__init__` files in Mercurial seems to be implemented
carefully.