pytype: add Python type annotations where necessary to guide pytype

Mute pytype warnings:

File "kallithea/lib/auth.py", line 142, in _cached_perms_data: No attribute 'DEFAULT_USER_ID' on module 'kallithea' [module-attr]
File "kallithea/lib/vcs/backends/base.py", line 73, in ...: No attribute '...' on BaseRepository [attribute-error]
File "kallithea/lib/vcs/backends/base.py", line 405, in ...: No attribute '...' on BaseChangeset [attribute-error]
File "kallithea/tests/api/api_base.py", line 2397, in test_api_get_changeset: No attribute 'TEST_REVISION' on _BaseTestApi [attribute-error]
File "kallithea/tests/api/api_base.py", line 2445, in test_api_get_pullrequest: No attribute 'TEST_PR_DST' on _BaseTestApi [attribute-error]
File "kallithea/tests/api/api_base.py", line 2445, in test_api_get_pullrequest: No attribute 'TEST_PR_SRC' on _BaseTestApi [attribute-error]
File "kallithea/tests/api/api_base.py", line 2467, in test_api_get_pullrequest: No attribute 'TEST_PR_REVISIONS' on _BaseTestApi [attribute-error]
File "kallithea/tests/api/api_base.py", line 67, in api_call: No attribute 'app' on _BaseTestApi [attribute-error]
File "kallithea/tests/base.py", line 154, in log_user: No attribute 'app' on TestController [attribute-error]
File "kallithea/tests/base.py", line 169, in _get_logged_user: No attribute '_logged_username' on TestController [attribute-error]

vcs: move changeset diff from controller to vcs

Remove unfortunate model dependency on controller ... and put the VCS details
where they belong, with less VCS specific knowledge in the controllers.

diff: fix two-way diff for added or removed files

Viewing the two-way diff of an added file gives following exception:

File "_base_root_html", line 211, in render_body

File "_base_base_html", line 42, in render_body

File "files_diff_2way_html", line 197, in render_main

File ".../kallithea/lib/vcs/nodes.py", line 411, in is_binary
return b'\0' in self.content
TypeError: 'in <string>' requires string as left operand, not bytes

At this point, self.content was '' (empty string).

Commit 9203621cae03a03bbf8cfb4b667daa656780a93e made that node content is
always bytes, but this also had to be reflected in EmptyChangeset.

Add a basic test that catches this behavior.

scripts: drop isort --wrap-length 160 - it is broken with py3 and not really necessary

Under Python 3, isort 4.3.21 failed with
https://github.com/timothycrosley/isort/issues/741 on
kallithea/controllers/api/api.py :

Traceback (most recent call last):
File "data/env/bin/isort", line 10, in <module>
sys.exit(main())
File ".../env/lib64/python3.7/site-packages/isort/main.py", line 379, in main
for sort_attempt in attempt_iterator:
File ".../env/lib64/python3.7/site-packages/isort/main.py", line 377, in <genexpr>
attempt_iterator = (sort_imports(file_name, **arguments) for file_name in file_names)
File ".../env/lib64/python3.7/site-packages/isort/main.py", line 88, in sort_imports
result = SortImports(file_name, **arguments)
File ".../env/lib64/python3.7/site-packages/isort/isort.py", line 207, in __init__
self._add_formatted_imports()
File ".../env/lib64/python3.7/site-packages/isort/isort.py", line 606, in _add_formatted_imports
self._add_from_imports(from_modules, section, section_output, sort_ignore_case)
File ".../env/lib64/python3.7/site-packages/isort/isort.py", line 526, in _add_from_imports
import_statement = self._multi_line_reformat(import_start, from_import_section, comments)
File ".../env/lib64/python3.7/site-packages/isort/isort.py", line 552, in _multi_line_reformat
dynamic_indent, indent, line_length, comments)
File ".../env/lib64/python3.7/site-packages/isort/isort.py", line 705, in _output_grid
if len(next_statement.split(self.line_separator)[-1]) + 1 > line_length:
TypeError: '>' not supported between instances of 'int' and 'str'

py3: remove safe_unicode in places where it no longer is needed because all strings (except bytes) already *are* unicode strings

(The remaining safe_unicode calls are still needed and can't just be removed,
generally because we in these cases still have to convert from bytes to unicode
strings.)

vcs: drop GitChangeset.id

It seems to be like raw_id, except the odd feature that it sometimes would
return 'tip'.

py3: drop __unicode__ ... and generally move towards just providing a good __repr__

We should never show str() (or similar) to end users.

vcs: change check_integrity to work on paths

Py3 failed because nodes can't be hashed.

vcs: replace __getslice__ with slice handling in __getitem__

Needed for py3.

vcs: fix __eq__ to return false if types are different

Follow up to ae12fabba699.

vcs: drop Repository.name_unicode

It wouldn't make much sense in py3 ... and is barely used.

api: add max_revisions option to get_changesets

The returning JSON can become pretty big and hard to parse.
Therefore add an option that allows a client to request the changesets in
smaller chuncks.

vcs: introduce 'branches' attribute on changesets, making it possible for Git to show multiple branches for a changeset

Mercurial changesets will always have have exactly one branch (which might be
"default"). The VCS data model was the same.

Git allows for a changeset to have 0 or more branches ... and possibly one of
them as active. The right data model is thus to have an enumerable of branches.

We thus add a 'branches' attribute and use it where applicable.

The existing 'branch' attribute used some heuristics to decide which branch use
as "the" branch ... and in some places code (and tests) rely on that. We thus
keep that old method, knowing that some of its uses probably should move to
'branches'.

The code for retrieving Git branches is based on work by Dominik Ruf.

api: wrap changeset file paths with safe_unicode

Fixes error in get_changesets if path contains non ascii character.

codingstyle: trivial whitespace fixes

Reported by flake8.

vcs: replace deprecated __getslice__ with __getitem__

__getslice__ has been deprecated since Python 2.0.

The support for single item indexing is currently unused, but was
trivial to implement (and needed for proper __getitem__ support).

indexers: use correct full repository name, which contains group name, at indexing

Before this revision, searching under the specific repository could
cause unexpected result, because repository names used for indexing didn't
contain the group name.

This issue was introduced by 8b7c0ef62427, which uses
repo.name_unicode as repository name instead of
safe_unicode(repo_name) to reduce unicode conversion cost while
repetition at indexing.

To use correct repository name at indexing, this revision replaces
repo.name_unicode by safe_unicode(repo_name). Reducing cost of repeated
unicode conversion cost while will (and should) be addressed in the
future.

This revision also adds a comment to BaseRepository.name property, to
avoid similar misunderstandings in the future.

vcs: fix repo size calculation

tip.walk already 'dives into' the dirs - don't do that twice.

cleanup: consistently use 'except ... as ...:'

Use the Python 2.6+ syntax instead of the old confusing 'except ..., ...'
syntax.

Second step in two-part process to rename directories.
This is the actual directory rename.