Add .editorconfig (#3001)

This was taken from the CoreFX repo verbatim, since we use the same
coding style. We can tweak it as appropriate (I'm thinking about
upgrading some suggestions to warnings, for example).

I already see some issues with it (e.g. insisting that we prefix statics
with `s_`, even for threadstatics - where we use `t_`).

Author: MichalStrehovsky

.editorconfig

@@ -0,0 +1,160 @@
+# editorconfig.org
+
+# top-most EditorConfig file
+root = true
+
+# Default settings:
+# A newline ending every file
+# Use 4 spaces as indentation
+[*]
+insert_final_newline = true
+indent_style = space
+indent_size = 4
+
+[project.json]
+indent_size = 2
+
+# C# files
+[*.cs]
+# New line preferences
+csharp_new_line_before_open_brace = all
+csharp_new_line_before_else = true
+csharp_new_line_before_catch = true
+csharp_new_line_before_finally = true
+csharp_new_line_before_members_in_object_initializers = true
+csharp_new_line_before_members_in_anonymous_types = true
+csharp_new_line_within_query_expression_clauses = true
+
+# Indentation preferences
+csharp_indent_block_contents = true
+csharp_indent_braces = false
+csharp_indent_case_contents = true
+csharp_indent_switch_labels = true
+csharp_indent_labels = flush_left
+
+# avoid this. unless absolutely necessary
+dotnet_style_qualification_for_field = false:suggestion
+dotnet_style_qualification_for_property = false:suggestion
+dotnet_style_qualification_for_method = false:suggestion
+dotnet_style_qualification_for_event = false:suggestion
+
+# only use var when it's obvious what the variable type is
+csharp_style_var_for_built_in_types = false:none
+csharp_style_var_when_type_is_apparent = false:none
+csharp_style_var_elsewhere = false:suggestion
+
+# use language keywords instead of BCL types
+dotnet_style_predefined_type_for_locals_parameters_members = true:suggestion
+dotnet_style_predefined_type_for_member_access = true:suggestion
+
+# name all constant fields using PascalCase
+dotnet_naming_rule.constant_fields_should_be_pascal_case.severity = suggestion
+dotnet_naming_rule.constant_fields_should_be_pascal_case.symbols  = constant_fields
+dotnet_naming_rule.constant_fields_should_be_pascal_case.style    = pascal_case_style
+
+dotnet_naming_symbols.constant_fields.applicable_kinds   = field
+dotnet_naming_symbols.constant_fields.required_modifiers = const
+
+dotnet_naming_style.pascal_case_style.capitalization = pascal_case
+
+# static fields should have s_ prefix
+dotnet_naming_rule.static_fields_should_have_prefix.severity = suggestion
+dotnet_naming_rule.static_fields_should_have_prefix.symbols  = static_fields
+dotnet_naming_rule.static_fields_should_have_prefix.style    = static_prefix_style
+
+dotnet_naming_symbols.static_fields.applicable_kinds   = field
+dotnet_naming_symbols.static_fields.required_modifiers = static
+
+dotnet_naming_style.static_prefix_style.required_prefix = s_
+dotnet_naming_style.static_prefix_style.capitalization = camel_case 
+
+# internal and private fields should be _camelCase
+dotnet_naming_rule.camel_case_for_private_internal_fields.severity = suggestion
+dotnet_naming_rule.camel_case_for_private_internal_fields.symbols  = private_internal_fields
+dotnet_naming_rule.camel_case_for_private_internal_fields.style    = camel_case_underscore_style
+
+dotnet_naming_symbols.private_internal_fields.applicable_kinds = field
+dotnet_naming_symbols.private_internal_fields.applicable_accessibilities = private, internal
+
+dotnet_naming_style.camel_case_underscore_style.required_prefix = _
+dotnet_naming_style.camel_case_underscore_style.capitalization = camel_case 
+
+# Code style defaults
+dotnet_sort_system_directives_first = true
+csharp_preserve_single_line_blocks = true
+csharp_preserve_single_line_statements = false
+
+# Expression-level preferences
+dotnet_style_object_initializer = true:suggestion
+dotnet_style_collection_initializer = true:suggestion
+dotnet_style_explicit_tuple_names = true:suggestion
+dotnet_style_coalesce_expression = true:suggestion
+dotnet_style_null_propagation = true:suggestion
+
+# Expression-bodied members
+csharp_style_expression_bodied_methods = false:none
+csharp_style_expression_bodied_constructors = false:none
+csharp_style_expression_bodied_operators = false:none
+csharp_style_expression_bodied_properties = true:none
+csharp_style_expression_bodied_indexers = true:none
+csharp_style_expression_bodied_accessors = true:none
+
+# Pattern matching
+csharp_style_pattern_matching_over_is_with_cast_check = true:suggestion
+csharp_style_pattern_matching_over_as_with_null_check = true:suggestion
+csharp_style_inlined_variable_declaration = true:suggestion
+
+# Null checking preferences
+csharp_style_throw_expression = true:suggestion
+csharp_style_conditional_delegate_call = true:suggestion
+
+# Space preferences
+csharp_space_after_cast = false
+csharp_space_after_colon_in_inheritance_clause = true
+csharp_space_after_comma = true
+csharp_space_after_dot = false
+csharp_space_after_keywords_in_control_flow_statements = true
+csharp_space_after_semicolon_in_for_statement = true
+csharp_space_around_binary_operators = before_and_after
+csharp_space_around_declaration_statements = do_not_ignore
+csharp_space_before_colon_in_inheritance_clause = true
+csharp_space_before_comma = false
+csharp_space_before_dot = false
+csharp_space_before_open_square_brackets = false
+csharp_space_before_semicolon_in_for_statement = false
+csharp_space_between_empty_square_brackets = false
+csharp_space_between_method_call_empty_parameter_list_parentheses = false
+csharp_space_between_method_call_name_and_opening_parenthesis = false
+csharp_space_between_method_call_parameter_list_parentheses = false
+csharp_space_between_method_declaration_empty_parameter_list_parentheses = false
+csharp_space_between_method_declaration_name_and_open_parenthesis = false
+csharp_space_between_method_declaration_parameter_list_parentheses = false
+csharp_space_between_parentheses = false
+csharp_space_between_square_brackets = false
+
+# C++ Files
+[*.{cpp,h,in}]
+curly_bracket_next_line = true
+indent_brace_style = Allman
+
+# Xml project files
+[*.{csproj,vcxproj,vcxproj.filters,proj,nativeproj,locproj}]
+indent_size = 2
+
+# Xml build files
+[*.builds]
+indent_size = 2
+
+# Xml files
+[*.{xml,stylecop,resx,ruleset}]
+indent_size = 2
+
+# Xml config files
+[*.{props,targets,config,nuspec}]
+indent_size = 2
+
+# Shell scripts
+[*.sh]
+end_of_line = lf
+[*.{cmd, bat}]
+end_of_line = crlf