Auto formatter config based on https://wiki.parity.io/Substrate-Style-Guide

rustfmt.toml

# This file encodes the formatting decisions expressed in https://wiki.parity.io/Substrate-Style-Guide

## Indent using tabs.
hard_tabs = true

## Lines should be longer than 100 characters long only in exceptional circumstances and certainly
## no longer than 120.
# max_width = 100 # default setting

## For this purpose, tabs are considered 4 characters wide.
# tab_spaces = 4 # default setting

## Indent levels should be greater than 5 only in exceptional circumstances and certainly no
## greater than 8. If they are greater than 5, then consider using let or auxiliary functions
## in order to strip out complex inline expressions.
# If this is to be enforced, it must be enforced manually for now.

## Never have spaces on a line prior to a non-whitespace character
# Ensured by "hard_tabs = true" option above

## Follow-on lines are only ever a single indent from the original line. Indent level should follow
## open parens/brackets, but should be collapsed to the smallest number of levels actually used.
# indent_style = "Block" # default setting

## Where is indented, and its items are indented one further.
# Not completely supported. The style guide calls for:
#
# fn foo<T>()
#     where
#         T: Bar
# {
# }
#
# but rustfmt does:
#
# fn foo<T>()
# where
#     T: Bar
# {
# }

## Argument lists or function invocations that are too long to fit on one line are indented
## similarly to code blocks, and once one param is indented in such a way, all others should
## be, too. Run-on parameter lists are also acceptable for single-line run-ons of basic function
## calls.
# this is default behaviour

## Always end last item of a multi-line comma-delimited set with , when legal.
# this is default behaviour

## Avoid trailing ;s where unneeded.
# In most cases, rustfmt follows this rule, with the exception of explicit return.
#
# if true {
#     return 1
# }
#
# is transformed into
#
# if true {
#     return 1;
# }

## Match arms may be either blocks or have a trailing , but not both.
# this is default behaviour

## Blocks should not be used unnecessarily.
# this is default behaviour

# Order of imports is not specified in the Substrate Style Guide. This option is set to false to
# match the current state of the codebase. reorder_imports can be enabled later
reorder_imports = false