Update docs, completion scripts for disable-legacy-registry

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit 2b8f0eef7338f37104464154ba65aef7db3b9703)
Signed-off-by: Tibor Vass <tibor@docker.com>

contrib/completion/zsh/_docker

@@ -2620,7 +2620,7 @@ __docker_subcommand() {
                 "($help)--default-gateway-v6[Container default gateway IPv6 address]:IPv6 address: " \
                 "($help)--default-shm-size=[Default shm size for containers]:size:" \
                 "($help)*--default-ulimit=[Default ulimits for containers]:ulimit: " \
-                "($help)--disable-legacy-registry[Disable contacting legacy registries]" \
+                "($help)--disable-legacy-registry[Disable contacting legacy registries (default true)]" \
                 "($help)*--dns=[DNS server to use]:DNS: " \
                 "($help)*--dns-opt=[DNS options to use]:DNS option: " \
                 "($help)*--dns-search=[DNS search domains to use]:DNS search: " \

docs/deprecated.md

@@ -292,7 +292,7 @@ of the `--changes` flag that allows to pass `Dockerfile` commands.
 
 **Target For Removal In Release: v17.12**
 
-Version 1.9 adds a flag (`--disable-legacy-registry=false`) which prevents the
+Version 1.8.3 added a flag (`--disable-legacy-registry=false`) which prevents the
 docker daemon from `pull`, `push`, and `login` operations against v1
 registries.  Though enabled by default, this signals the intent to deprecate
 the v1 protocol.

docs/reference/commandline/dockerd.md

@@ -42,7 +42,7 @@ Options:
       --default-gateway-v6 ip                 Container default gateway IPv6 address
       --default-runtime string                Default OCI runtime for containers (default "runc")
       --default-ulimit ulimit                 Default ulimits for containers (default [])
-      --disable-legacy-registry               Disable contacting legacy registries
+      --disable-legacy-registry               Disable contacting legacy registries (default true)
       --dns list                              DNS server to use (default [])
       --dns-opt list                          DNS options to use (default [])
       --dns-search list                       DNS search domains to use (default [])
@@ -901,7 +901,18 @@ system's list of trusted CAs instead of enabling `--insecure-registry`.
 
 ##### Legacy Registries
 
-Enabling `--disable-legacy-registry` forces a docker daemon to only interact with registries which support the V2 protocol.  Specifically, the daemon will not attempt `push`, `pull` and `login` to v1 registries.  The exception to this is `search` which can still be performed on v1 registries.
+Operations against registries supporting only the legacy v1 protocol are
+disabled by default. Specifically, the daemon will not attempt `push`,
+`pull` and `login` to v1 registries. The exception to this is `search`
+which can still be performed on v1 registries.
+
+Add `"disable-legacy-registry":false` to the [daemon configuration
+file](#daemon-configuration-file), or set the
+`--disable-legacy-registry=false` flag, if you need to interact with
+registries that have not yet migrated to the v2 protocol.
+
+Interaction v1 registries will no longer be supported in Docker v17.12,
+and the `disable-legacy-registry` configuration option will be removed.
 
 #### Running a Docker daemon behind an HTTPS_PROXY
 

man/dockerd.8.md

@@ -192,7 +192,7 @@ $ sudo dockerd --add-runtime runc=runc --add-runtime custom=/usr/local/bin/my-ru
   Default ulimits for containers.
 
 **--disable-legacy-registry**=*true*|*false*
-  Disable contacting legacy registries
+  Disable contacting legacy registries. Default is `true`.
 
 **--dns**=""
   Force Docker to use specific DNS servers