Blacksin

- don't populate the cache on `--check` (175)

- added a "cache"; files already reformatted that haven't changed on disk won't be
reformatted again (109)

- `--check` and `--diff` are no longer mutually exclusive (149)

- generalized star expression handling, including double stars; this fixes
multiplication making expressions "unsafe" for trailing commas (132)

- _Black_ no longer enforces putting empty lines behind control flow statements (90)

- _Black_ now splits imports like "Mode 3 + trailing comma" of isort (127)

- fixed comment indentation when a standalone comment closes a block (16, 32)

- fixed standalone comments receiving extra empty lines if immediately preceding a
class, def, or decorator (56, 154)

- fixed `--diff` not showing entire path (130)

- fixed parsing of complex expressions after star and double stars in function calls
(2)

- fixed invalid splitting on comma in lambda arguments (133)

- fixed missing splits of ternary expressions (141)

- fixed parsing of unaligned standalone comments (99, 112)

- fixed placement of dictionary unpacking inside dictionary literals (111)

- Vim plugin now works on Windows, too

- fixed unstable formatting when encountering unnecessarily escaped quotes in a string
(120)

- added `--quiet` (78)

- added automatic parentheses management (4)

- added [pre-commit](https://pre-commit.com) integration (103, 104)

- fixed reporting on `--check` with multiple files (101, 102)

- fixed removing backslash escapes from raw strings (100, 105)

- added `--diff` (87)

- add line breaks before all delimiters, except in cases like commas, to better comply
with PEP 8 (73)

- standardize string literals to use double quotes (almost) everywhere (75)

- fixed handling of standalone comments within nested bracketed expressions; _Black_
will no longer produce super long lines or put all standalone comments at the end of
the expression (22)

- fixed 18.3a4 regression: don't crash and burn on empty lines with trailing whitespace
(80)

- fixed 18.3a4 regression: ` yapf: disable` usage as trailing comment would cause
_Black_ to not emit the rest of the file (95)

- when CTRL+C is pressed while formatting many files, _Black_ no longer freaks out with
a flurry of asyncio-related exceptions

- only allow up to two empty lines on module level and only single empty lines within
functions (74)

- ` fmt: off` and ` fmt: on` are implemented (5)

- automatic detection of deprecated Python 2 forms of print statements and exec
statements in the formatted file (49)

- use proper spaces for complex expressions in default values of typed function
arguments (60)

- only return exit code 1 when --check is used (50)

- don't remove single trailing commas from square bracket indexing (59)

- don't omit whitespace if the previous factor leaf wasn't a math operator (55)

- omit extra space in kwarg unpacking if it's the first argument (46)

- omit extra space in
[Sphinx auto-attribute comments](http://www.sphinx-doc.org/en/stable/ext/autodoc.htmldirective-autoattribute)
(68)