Add doc for global Jib configuration

docs/faq.md

@@ -28,9 +28,11 @@ If a question you have is not answered below, please [submit an issue](/../../is
 [How can I inspect the image Jib built?](#how-can-i-inspect-the-image-jib-built)\
 [I would like to run my application with a javaagent.](#i-would-like-to-run-my-application-with-a-javaagent)\
 [How can I tag my image with a timestamp?](#how-can-i-tag-my-image-with-a-timestamp)\
-[How do I specify a platform in the manifest list (or OCI index) of a base image?](#how-do-i-specify-a-platform-in-the-manifest-list-or-oci-index-of-a-base-image) \
-[I want to exclude files from layers, have more fine-grained control over layers, change file ownership, etc.](#i-want-to-exclude-files-from-layers-have-more-fine-grained-control-over-layers-change-file-ownership-etc) \
-[Jib build plugins don't have the feature that I need.](#jib-build-plugins-dont-have-the-feature-that-i-need)
+[How do I specify a platform in the manifest list (or OCI index) of a base image?](#how-do-i-specify-a-platform-in-the-manifest-list-or-oci-index-of-a-base-image)\
+[I want to exclude files from layers, have more fine-grained control over layers, change file ownership, etc.](#i-want-to-exclude-files-from-layers-have-more-fine-grained-control-over-layers-change-file-ownership-etc)\
+[Jib build plugins don't have the feature that I need.](#jib-build-plugins-dont-have-the-feature-that-i-need)\
+[I am hitting Docker Hub rate limits. How can I configure registry mirrors?](#i-am-hitting-docker-hub-rate-limits-how-can-i-configure-registry-mirrors)\
+[Where is the global Jib configuration file and how I can configure it?](#where-is-the-global-jib-configuration-file-and-how-i-can-configure-it)
 
 **Build Problems**\
 [How can I diagnose problems pulling or pushing from remote registries?](#how-can-i-diagnose-problems-pulling-or-pushing-from-remote-registries)\
@@ -549,6 +551,14 @@ See ["Jib build plugins don't have the feature that I need"](#jib-build-plugins-
 
 The Jib build plugins have an extension framework that enables anyone to easily extend Jib's behavior to their needs. We maintain select [first-party](https://github.com/GoogleContainerTools/jib-extensions/tree/master/first-party) plugins for popular use cases like [fine-grained layer control](https://github.com/GoogleContainerTools/jib-extensions/tree/master/first-party/jib-layer-filter-extension-gradle) and [Quarkus support](https://github.com/GoogleContainerTools/jib-extensions/tree/master/first-party/jib-quarkus-extension-gradle), but anyone can write and publish an extension. Check out the [jib-extensions](https://github.com/GoogleContainerTools/jib-extensions) repository for more information.
 
+### I am hitting Docker Hub rate limits. How can I configure registry mirrors?
+
+See the [Maven](https://github.com/GoogleContainerTools/jib/tree/global-config-doc/jib-maven-plugin#global-jib-configuration) and [Gradle](https://github.com/GoogleContainerTools/jib/tree/global-config-doc/jib-gradle-plugin#global-jib-configuration) docs. Note that the example in the docs uses [Google's Docker Hub mirror on `mirror.gcr.io`](https://cloud.google.com/container-registry/docs/pulling-cached-images).
+
+### Where is the global Jib configuration file and how I can configure it?
+
+See the [Maven](https://github.com/GoogleContainerTools/jib/tree/global-config-doc/jib-maven-plugin#global-jib-configuration) and [Gradle](https://github.com/GoogleContainerTools/jib/tree/global-config-doc/jib-gradle-plugin#global-jib-configuration) docs.
+
 
 ## Build Problems
 

jib-gradle-plugin/README.md

@@ -28,6 +28,7 @@ For information about the project, see the [Jib project README](../README.md).
 * [Multi Module Projects](#multi-module-projects)
 * [Extended Usage](#extended-usage)
   * [System Properties](#system-properties)
+  * [Global Jib Configuration](#global-jib-configuration)
   * [Example](#example)
   * [Adding Arbitrary Files to the Image](#adding-arbitrary-files-to-the-image)
   * [Authentication Methods](#authentication-methods)
@@ -311,6 +312,35 @@ Property | Type | Default | Description
  * *Mac: `[cache root]/Google/Jib/`, where `[cache root]` is `$XDG_CACHE_HOME` (`$HOME/Library/Caches/` if not set)*
  * *Windows: `[cache root]\Google\Jib\Cache`, where `[cache root]` is `$XDG_CACHE_HOME` (`%LOCALAPPDATA%` if not set)*
 
+### Global Jib Configuration
+
+Some options can be set in the global Jib configuration file. The file is at the following locations on each platform:
+
+* *Linux: `[config root]/google-cloud-tools-java/jib/config.json`, where `[config root]` is `$XDG_CONFIG_HOME` (`$HOME/.config/` if not set)*
+* *Mac: `[config root]/Google/Jib/config.json`, where `[config root]` is `$XDG_CONFIG_HOME` (`$HOME/Library/Preferences/Config/` if not set)*
+* *Windows: `[config root]\Google\Jib\Config\config.json`, where `[config root]` is `$XDG_CONFIG_HOME` (`%LOCALAPPDATA%` if not set)*
+
+#### Properties 
+
+* `disableUpdateCheck`: when set to true, disables the periodic up-to-date version check.
+* `registryMirrors`: a list of mirror settings for each base image registry. In the following example, if the base image configured in Jib is for a Docker Hub image, then `mirror.gcr.io`, `localhost:5000`, and the Docker Hub (`registry-1.docker.io`) are tried in order until Jib can successfuly pull a base image.
+
+```json
+{
+  "disableUpdateCheck": false,
+  "registryMirrors": [
+    {
+      "registry": "registry-1.docker.io",
+      "mirrors": ["mirror.gcr.io", "localhost:5000"]
+    },
+    {
+      "registry": "quay.io",
+      "mirrors": ["private-mirror.test.com"]
+    }
+  ]
+}
+```
+
 ### Example
 
 In this configuration, the image:

jib-maven-plugin/README.md

@@ -28,6 +28,7 @@ For information about the project, see the [Jib project README](../README.md).
 * [Multi Module Projects](#multi-module-projects)
 * [Extended Usage](#extended-usage)
   * [System Properties](#system-properties)
+  * [Global Jib Configuration](#global-jib-configuration)
   * [Example](#example)
   * [Adding Arbitrary Files to the Image](#adding-arbitrary-files-to-the-image)
   * [Authentication Methods](#authentication-methods)
@@ -359,6 +360,35 @@ Property | Type | Default | Description
  * *Mac: `[cache root]/Google/Jib/`, where `[cache root]` is `$XDG_CACHE_HOME` (`$HOME/Library/Caches/` if not set)*
  * *Windows: `[cache root]\Google\Jib\Cache`, where `[cache root]` is `$XDG_CACHE_HOME` (`%LOCALAPPDATA%` if not set)*
 
+### Global Jib Configuration
+
+Some options can be set in the global Jib configuration file. The file is at the following locations on each platform:
+
+* *Linux: `[config root]/google-cloud-tools-java/jib/config.json`, where `[config root]` is `$XDG_CONFIG_HOME` (`$HOME/.config/` if not set)*
+* *Mac: `[config root]/Google/Jib/config.json`, where `[config root]` is `$XDG_CONFIG_HOME` (`$HOME/Library/Preferences/Config/` if not set)*
+* *Windows: `[config root]\Google\Jib\Config\config.json`, where `[config root]` is `$XDG_CONFIG_HOME` (`%LOCALAPPDATA%` if not set)*
+
+#### Properties 
+
+* `disableUpdateCheck`: when set to true, disables the periodic up-to-date version check.
+* `registryMirrors`: a list of mirror settings for each base image registry. In the following example, if the base image configured in Jib is for a Docker Hub image, then `mirror.gcr.io`, `localhost:5000`, and the Docker Hub (`registry-1.docker.io`) are tried in order until Jib can successfuly pull a base image.
+
+```json
+{
+  "disableUpdateCheck": false,
+  "registryMirrors": [
+    {
+      "registry": "registry-1.docker.io",
+      "mirrors": ["mirror.gcr.io", "localhost:5000"]
+    },
+    {
+      "registry": "quay.io",
+      "mirrors": ["private-mirror.test.com"]
+    }
+  ]
+}
+```
+
 ### Example
 
 In this configuration, the image: