tests: check import cycles in hgext/**.py, too It is important to realize existing cycles in hgext/**.py.

import-checker: don't treat modules as relative one if not found The previous patch ensures all module names are recorded in `imports` as absolute names, so we no longer need to treat modules as ones imported relatively from the target source if they appear to not be from the stdlib.

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.

import-checker: add utility to examine what module is imported easily `fromlocalfunc()` uses: - `modulename` (of the target source) to compose absolute module name imported relatively from it It is assumed that `modulename` is an `dotted_name_of_path()`-ed source file, which may have `.__init__` at the end of it. This assumption makes composing `prefix` of relative name easy. - `localmods` to examine whether there is a locally defined (= Mercurial specific) module matching against the specified name It is assumed that module names not existing in `localmods` are ones of Python standard library.

subrepo: further replacement of try/except with 'next' Burn StopIteration, Burn!

parsers: use 'next' instead of try/except This get rid of another StopIteration abomination. The change in self.current value is supposed to not matter as nobody should be calling '_advance' after that (as per Matt wisdom).

dagparser: use 'next' instead of try/except for default value "Ich liebe es wenn ein Plan funktioniert."

getlogrevs: rewrite a loop to get read of try/except Get rid of the 'except StopIteration' abomination.

_makelogrevset: replace try/except with 'next' usage More readable without the 'except StopIteration' abomination.

ignore: move readpatternfile to match.py In preparation for adding 'include:' rule support to match.py, let's move the pattern file reader function to match.py