Add support for a global configuration file.

doc/configuration.md

Index: doc/configuration.md
diff --git a/doc/package_config.md b/doc/configuration.md
similarity index 91%
copy from doc/package_config.md
copy to doc/configuration.md
index 974e7ce98269bd8a3ed418d125ae44fb60b52160..9099528b2171d15524153bce591b71b9d687f8f6 100644
--- a/doc/package_config.md
+++ b/doc/configuration.md
@@ -51,6 +51,7 @@ tags:
 * [Configuration Presets](#configuration-presets)
   * [`presets`](#presets)
   * [`add_preset`](#add_preset)
+* [Global Configuration](#global-configuration)
 
 ## Test Configuration
 
@@ -121,6 +122,9 @@ tags:
     skip: "Our Chrome launcher is busted. See issue 1234."
 ```
 
+This field is not supported in the
+[global configuration file](#global-configuration).
+
 ### `test_on`
 
 This field declares which platforms a test supports. It takes a
@@ -147,6 +151,9 @@ warning and skip that platform.
 test_on: vm
 ```
 
+This field is not supported in the
+[global configuration file](#global-configuration).
+
 ## Runner Configuration
 
 Unlike [test configuration](#test-configuration), runner configuration affects
@@ -169,6 +176,9 @@ paths:
 - test/middling
 ```
 
+This field is not supported in the
+[global configuration file](#global-configuration).
+
 ### `filename`
 
 This field indicates the filename pattern that the test runner uses to find test
@@ -186,6 +196,9 @@ filename: "test_*.dart"
 
 [glob syntax]: https://github.com/dart-lang/glob#syntax
 
+This field is not supported in the
+[global configuration file](#global-configuration).
+
 ### `names`
 
 This field causes the runner to only run tests whose names match the given
@@ -205,6 +218,9 @@ presets:
     - "[Cc]hrome"
 ```
 
+This field is not supported in the
+[global configuration file](#global-configuration).
+
 ### `plain_names`
 
 This field causes the runner to only run tests whose names contain the given
@@ -223,6 +239,9 @@ presets:
     - "Internet Explorer"
 ```
 
+This field is not supported in the
+[global configuration file](#global-configuration).
+
 ### `include_tags`
 
 This field causes the runner to only run tests whose tags match the given
@@ -241,6 +260,9 @@ presets:
     include_tags: !browser || content-shell
 ```
 
+This field is not supported in the
+[global configuration file](#global-configuration).
+
 ### `exclude_tags`
 
 This field causes the runner not to run tests whose tags match the given
@@ -257,6 +279,9 @@ presets:
     exclude_tags: browser && !content-shell
 ```
 
+This field is not supported in the
+[global configuration file](#global-configuration).
+
 ### `platforms`
 
 This field indicates which platforms tests should run on by default. It allows
@@ -323,6 +348,9 @@ beyond me). It defaults to "expanded" on Windows and "compact" everywhere else.
 reporter: expanded
 ```
 
+This field is not supported in the
+[global configuration file](#global-configuration).
+
 ## Configuring Tags
 
 ### `tags`
@@ -378,7 +406,8 @@ configurations, the test runner *does not guarantee* what order they'll be
 resolved in. In practice, conflicting configuration is pretty unlikely and it's
 easy to just explicitly specify what you want on the test itself.
 
-This field counts as [test configuration](#test-configuration).
+This field counts as [test configuration](#test-configuration). It is not
+supported in the [global configuration file](#global-configuration).
 
 ### `add_tags`
 
@@ -402,6 +431,9 @@ tags:
   ie: {add_tags: [browser]}
 ```
 
+This field is not supported in the
+[global configuration file](#global-configuration).
+
 ## Configuring Platforms
 
 There are two different kinds of platform configuration.
@@ -529,3 +561,15 @@ presets:
     filename: "chrome_*_test.dart"
     add_presets: [browser]
 ```
+
+## Global Configuration
+
+The test runner also supports a global configuration file. On Windows, this
+file's local defaults to `%LOCALAPPDATA%\DartTest.yaml`. On Unix, it defaults to
+`~/.dart_test.yaml`. It can also be explicitly set using the `DART_TEST_CONFIG`
+environment variable.
+
+The global configuration file supports a subset of the fields supported by the
+package-specific configuration file. In general, it doesn't support fields that
+are closely tied to the structure of an individual package. Fields that are not
+supported in the global configuration file say so in their documentation.