[ACR] Add a new argument '--expose-token' for 'az acr login'

src/azure-cli/azure/cli/command_modules/acr/_help.py

@@ -257,11 +257,14 @@
 helps['acr login'] = """
 type: command
 short-summary: Log in to an Azure Container Registry through the Docker CLI.
-long-summary: Docker must be installed on your machine. Once done, use 'docker logout <registry url>' to log out.
+long-summary: Docker must be installed on your machine. Once done, use 'docker logout <registry url>' to log out. (If you only need an access token and do not want to install Docker, specify '--expose-token')
 examples:
   - name: Log in to an Azure Container Registry
     text: >
         az acr login -n MyRegistry
+  - name: Get an Azure Container Registry access token
+    text: >
+        az acr login -n MyRegistry --expose-token
 """
 
 helps['acr network-rule'] = """

src/azure-cli/azure/cli/command_modules/acr/_params.py

@@ -93,6 +93,7 @@ def load_arguments(self, _):  # pylint: disable=too-many-statements
 
     with self.argument_context('acr login') as c:
         c.argument('resource_group_name', deprecate_info=c.deprecate(hide=True))
+        c.argument('expose_token', options_list=['--expose-token', '-t'], help='Expose access token instead of automatically logging in through Docker CLI', action='store_true', is_preview=True)
 
     with self.argument_context('acr repository') as c:
         c.argument('resource_group_name', deprecate_info=c.deprecate(hide=True))

src/azure-cli/azure/cli/command_modules/acr/custom.py

@@ -14,7 +14,7 @@
     get_resource_group_name_by_registry_name,
     user_confirmation
 )
-from ._docker_utils import get_login_credentials
+from ._docker_utils import get_login_credentials, EMPTY_GUID
 from .network_rule import NETWORK_RULE_NOT_SUPPORTED
 
 logger = get_logger(__name__)
@@ -129,12 +129,39 @@ def acr_login(cmd,
               resource_group_name=None,  # pylint: disable=unused-argument
               tenant_suffix=None,
               username=None,
-              password=None):
+              password=None,
+              expose_token=False):
+    if expose_token:
+        login_server, _, password = get_login_credentials(
+            cmd=cmd,
+            registry_name=registry_name,
+            tenant_suffix=tenant_suffix,
+            username=username,
+            password=password)
+
+        logger.warning("You can perform manual login using the provided access token below, "
+                       "for example: 'docker login loginServer -u %s -p accessToken'", EMPTY_GUID)
+
+        token_info = {
+            "loginServer": login_server,
+            "accessToken": password
+        }
+
+        return token_info
+
+    tips = "You may want to use 'az acr login -n {} --expose-token' to get an access token, " \
+           "which does not require Docker to be installed.".format(registry_name)
+
     from azure.cli.core.util import in_cloud_console
     if in_cloud_console():
-        raise CLIError('This command requires running the docker daemon, which is not supported in Azure Cloud Shell.')
+        raise CLIError("This command requires running the docker daemon, "
+                       "which is not supported in Azure Cloud Shell. " + tips)
 
-    docker_command, _ = get_docker_command()
+    try:
+        docker_command, _ = get_docker_command()
+    except CLIError as e:
+        logger.warning(tips)
+        raise e
 
     login_server, username, password = get_login_credentials(
         cmd=cmd,
@@ -174,6 +201,8 @@ def acr_login(cmd,
             output = getattr(sys.stderr, 'buffer', sys.stderr)
             output.write(stderr)
 
+    return None
+
 
 def acr_show_usage(cmd, client, registry_name, resource_group_name=None):
     _, resource_group_name = validate_managed_registry(cmd,