.rustfmt.toml with all configs, descriptions, parameters and defaults for version 0.7.1 of rustfmt.

.rustfmt.toml

# ----------------------------------------------------------------------------------
#                      r u s t f m t   -   C O N F I G
# ==================================================================================
# 
# Version: 0.7.1
# Author : Robbepop <robbepop@web.de>
# 
# A predefined .rustfmt.toml file with all configuration options and their
# associated description, possible values and default values for use in other
# projects.
# 
# This should actually automatically be shipped with cargo fmt or rustfmt itself!
# ----------------------------------------------------------------------------------

# Use verbose output.
# Default: false
#   verbose = 

# Do not reformat out of line modules.
# Default: false
#   skip_children = 

# Lines to format; this is not supported in rustfmt.toml,
# and can only be specified via the --file-lines option.
#   file_lines = 

# Maximum width of each line.
# Default: 100
#   max_width = 

# Ideal width of each line.
# Default: 80
#   max_width = 

# Number of spaces per tab.
# Default: 4
  # tab_spaces = 

# Maximum width of the args of a function call before
# falling back to vertical formatting.
# Default: 60
#   fn_call_width = 

# Maximum width in the body of a struct lit before falling back to vertical formatting.
# Default: 16
#   struct_lit_width = 

# Maximum width in the body of a struct variant before falling back to vertical formatting.
# Default: 35
#   struct_variant_width = 

# Always print the abi for extern items.
# Default: true
#   force_explicit_abi = 

# Unix or Windows line endings.
# Values: Windows | Unix | Native
# Default: Unix
#   newline_style = 

# Brace style for functions.
# Values: AlwaysNextLine | PreferSameLine | SameLineWhere
# Default: SameLineWhere
#   fn_brace_style = 

# Brace style for structs and enums.
# Values: AlwaysNextLine | PreferSameLine | SameLineWhere
# Default: SameLineWhere
#   item_brace_style = 

# Brace style for control flow construct.
# Values: AlwaysSameLine | ClosingNextLine | AlwaysNextLine
# Default: AlwaysSameLine
#   control_brace_style = 

# Put empty-body implementations on a single line.
# Default: true
#   impl_empty_single_line = 

# Put empty-body functions on a single line.
# Default: true
#   fn fn_empty_single_line = 

# Put single-expression functions on a single line.
# Default: false
#   fn_single_line = 

# Location of return type in function declaration.
# Values: WithArgs | WithWhereClause
# Default: WithArgs
#   fn_return_indent = 

# If function argument parenthesis goes on a newline.
# Default: true
#   fn_args_paren_newline = 

# Argument density in functions.
# Values: Compressed | Tall | CompressedIfEmpty | Vertical
# Default: Tall
#   fn_args_density = 

# Layout of function arguments.
# Values: Visual | Block | BlockAlways
# Default: Visual
#   fn_args_layout = 

# Indent on function arguments.
# Values: Inherit | Tabbed | Visual
# Default: Visual
#   fn_arg_indent = 

# Determines if '+' or '=' are wrapped in spaces in the punctuation of types.
# Values: Compressed | Wide
# Default: Wide
#   type_punctuation_density = 

# Density of a where clause.
# Values: Compressed | Tall | CompressedIfEmpty | Vertical
# Default: CompressedIfEmpty
#   where_density = 

# Indentation of a where clause.
# Values: Inherit | Tabbed | Visual
# Default: Tabbed
#   where_indent = 

# Element layout inside a where clause.
# Values: Vertical | Horizontal | HorizontalVertical | Mixed
# Default: Vertical
#   where_layout = 

# Indentation style of a where predicate.
# Values: Inherit | Tabbed | Visual
# Default: Visual
#   where_pred_indent = 

# Put a trailing comma on where clauses.
# Default: false
#   where_trailing_comma = 

# Indentation of generics.
# Values: Inherit | Tabbed | Visual
# Default: Visual
#   generics_indent = 

# If there is a trailing comma on structs.
# Values: Always | Never | Vertical
# Default: Vertical
#   struct_trailing_comma = 

# If there is a trailing comma on literal structs.
# Values: Always | Never | Vertical
# Default: Vertical
#   struct_lit_trailing_comma = 

# Style of struct definition.
# Values: Visual | Block
# Default: Block
#   struct_lit_style = 

# Multiline style on literal structs.
# Values: PreferSingle | ForceMulti
# Default: PreferSingle
#   struct_lit_multiline_style = 

# Put a trailing comma on enum declarations.
# Default: true
#   enum_trailing_comma = 

# Report all, none or unnumbered occurrences of TODO in source file comments.
# Values: Always | Unnumbered | Never
# Default: Never
#   report_todo = 

# Report all, none or unnumbered occurrences of FIXME in source file comments.
# Values: Always | Unnumbered | Never
# Default: Never
#   report_fixme = 

# Indent on chain base.
# Values: Inherit | Tabbed | Visual
# Default: Tabbed
#   chain_base_indent = 

# Indentation of chain.
# Values: Inherit | Tabbed | Visual
# Default: Tabbed
#   chain_indent = 

# Allow last call in method chain to break the line.
# Default: true
#   chains_overflow_last = 

# Reorder import statements alphabetically.
# Default: false
#   reorder_imports = 

# Reorder lists of names in import statements alphabetically.
# Default: false
#   reorder_imported_names = 

# Maximum line length for single line if-else expressions.
# A value of zero means always break if-else expressions.
# Default: 50
#   single_line_if_else_max_width = 

# Format string literals where necessary.
# Default: true
#   format_strings = 

# Always format string literals.
# Default: false
#   force_format_strings = 

# Retain some formatting characteristics from the source code.
# Default: true
#   take_source_hints = 

# Use tab characters for indentation, spaces for alignment.
# Default: false
#   hard_tabs = 

# Break comments to fit on the line.
# Default: false
#   wrap_comments = 

# Convert /* */ comments to // comments where possible.
# Default: false
#   normalize_comments = 

# Wrap multiline match arms in blocks.
# Default: true
#   wrap_match_arms = 

# Put a trailing comma after a block based match arm (non-block arms are not affected).
# Default: false
#   match_block_trailing_comma = 

# Put a trailing comma after a wildcard arm.
# Default: true
#   match_wildcard_trailing_comma = 

# How many lines a closure must have before it is block indented.
# -1 means never use block indent.
# Type: <signed integer>
# Default: 5
#   closure_block_indent_threshold = 

# Leave a space before the colon in a type annotation.
# Default: false
#   space_before_type_annotation = 

# Leave a space after the colon in a type annotation.
# Default: true
#   space_after_type_annotation_colon = 

# Leave a space before the colon in a trait or lifetime bound.
# Default: false
#   space_before_bound = 

# Leave a space after the colon in a trait or lifetime bound.
# Default: true
#   space_after_bound_colon = 

# Put spaces around the  .. and ... range operators.
# Default: false
#   spaces_around_ranges = 

# Put spaces within non-empty generic arguments.
# Default: false
#   spaces_within_angle_brackets = 

# Put spaces within non-empty square brackets.
# Default: false
#   spaces_within_square_brackets = 

# Put spaces within non-empty parentheses.
# Default: false
#   spaces_within_parens = 

# Replace uses of the try! macro by the ? shorthand.
# Default: false
#   use_try_shorthand = 

# What Write Mode to use when none is supplied: Replace, Overwrite, Display, Diff, Coverage.
# Values: Replace | Overwrite | Display | Diff | Coverage | Plain | Checkstyle
# Default: Replace
#   write_mode = 

# Replace strings of _ wildcards by a single .. in tuple patterns.
# Default: false
#   condense_wildcard_suffices = 

where_pred_indent is wrong, has to be either Visual or Block

Warning: Unknown configuration option 'write_mode'

This is outdated!
Since recent versions rustfmt supports --print-config to print the config.
Just type in rustfmt --print-config default for all default configurations.
For a description for all configurations visit: https://github.com/rust-lang/rustfmt/blob/master/Configurations.md

Thanks Robbepop! But the format of your file is superior! It's nice to see the options and descriptions in the file itself. It would be nice if rustfmt could generate the additional context that yours contains.

Missing ignore, aren't we?