Update documentation and change log to include the preliminary validation of dockerfile.

This commit updates documentation and change log to include
the preliminary validation of the dockerfile before instructions
in dockerfile is run one-by-one.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

docs/reference/api/docker_remote_api.md

@@ -123,6 +123,7 @@ This section lists each version from latest to oldest.  Each listing includes a
 * `POST /containers/create/` and `POST /containers/(name)/update` now validates restart policies.
 * `POST /containers/create` now validates IPAMConfig in NetworkingConfig, and returns error for invalid IPv4 and IPv6 addresses (`--ip` and `--ip6` in `docker create/run`).
 * `POST /containers/create` now takes a `Mounts` field in `HostConfig` which replaces `Binds` and `Volumes`. *note*: `Binds` and `Volumes` are still available but are exclusive with `Mounts`
+* `POST /build` now performs a preliminary validation of the `Dockerfile` before starting the build, and returns an error if the syntax is incorrect. Note that this change is _unversioned_ and applied to all API versions.
 
 ### v1.24 API changes
 

docs/reference/api/docker_remote_api_v1.18.md

@@ -1201,6 +1201,10 @@ The archive may include any number of other files,
 which are accessible in the build context (See the [*ADD build
 command*](../../reference/builder.md#add)).
 
+The Docker daemon performs a preliminary validation of the `Dockerfile` before
+starting the build, and returns an error if the syntax is incorrect. After that,
+each instruction is run one-by-one until the ID of the new image is output.
+
 The build is canceled if the client drops the connection by quitting
 or being killed.
 

docs/reference/api/docker_remote_api_v1.19.md

@@ -1243,6 +1243,10 @@ The archive may include any number of other files,
 which are accessible in the build context (See the [*ADD build
 command*](../../reference/builder.md#add)).
 
+The Docker daemon performs a preliminary validation of the `Dockerfile` before
+starting the build, and returns an error if the syntax is incorrect. After that,
+each instruction is run one-by-one until the ID of the new image is output.
+
 The build is canceled if the client drops the connection by quitting
 or being killed.
 

docs/reference/api/docker_remote_api_v1.20.md

@@ -1370,6 +1370,10 @@ The archive may include any number of other files,
 which are accessible in the build context (See the [*ADD build
 command*](../../reference/builder.md#add)).
 
+The Docker daemon performs a preliminary validation of the `Dockerfile` before
+starting the build, and returns an error if the syntax is incorrect. After that,
+each instruction is run one-by-one until the ID of the new image is output.
+
 The build is canceled if the client drops the connection by quitting
 or being killed.
 

docs/reference/api/docker_remote_api_v1.21.md

@@ -1448,6 +1448,10 @@ The archive may include any number of other files,
 which are accessible in the build context (See the [*ADD build
 command*](../../reference/builder.md#add)).
 
+The Docker daemon performs a preliminary validation of the `Dockerfile` before
+starting the build, and returns an error if the syntax is incorrect. After that,
+each instruction is run one-by-one until the ID of the new image is output.
+
 The build is canceled if the client drops the connection by quitting
 or being killed.
 

docs/reference/api/docker_remote_api_v1.22.md

@@ -1625,6 +1625,10 @@ The archive may include any number of other files,
 which are accessible in the build context (See the [*ADD build
 command*](../../reference/builder.md#add)).
 
+The Docker daemon performs a preliminary validation of the `Dockerfile` before
+starting the build, and returns an error if the syntax is incorrect. After that,
+each instruction is run one-by-one until the ID of the new image is output.
+
 The build is canceled if the client drops the connection by quitting
 or being killed.
 

docs/reference/api/docker_remote_api_v1.23.md

@@ -1658,6 +1658,10 @@ The archive may include any number of other files,
 which are accessible in the build context (See the [*ADD build
 command*](../../reference/builder.md#add)).
 
+The Docker daemon performs a preliminary validation of the `Dockerfile` before
+starting the build, and returns an error if the syntax is incorrect. After that,
+each instruction is run one-by-one until the ID of the new image is output.
+
 The build is canceled if the client drops the connection by quitting
 or being killed.
 

docs/reference/api/docker_remote_api_v1.24.md

@@ -1661,6 +1661,10 @@ The archive may include any number of other files,
 which are accessible in the build context (See the [*ADD build
 command*](../../reference/builder.md#add)).
 
+The Docker daemon performs a preliminary validation of the `Dockerfile` before
+starting the build, and returns an error if the syntax is incorrect. After that,
+each instruction is run one-by-one until the ID of the new image is output.
+
 The build is canceled if the client drops the connection by quitting
 or being killed.
 

docs/reference/api/docker_remote_api_v1.25.md

@@ -1682,6 +1682,10 @@ The archive may include any number of other files,
 which are accessible in the build context (See the [*ADD build
 command*](../../reference/builder.md#add)).
 
+The Docker daemon performs a preliminary validation of the `Dockerfile` before
+starting the build, and returns an error if the syntax is incorrect. After that,
+each instruction is run one-by-one until the ID of the new image is output.
+
 The build is canceled if the client drops the connection by quitting
 or being killed.
 

docs/reference/builder.md

@@ -68,6 +68,13 @@ add multiple `-t` parameters when you run the `build` command:
 
     $ docker build -t shykes/myapp:1.0.2 -t shykes/myapp:latest .
 
+Before the Docker daemon runs the instructions in the `Dockerfile`, it performs
+a preliminary validation of the `Dockerfile` and returns an error if the syntax is incorrect:
+
+    $ docker build -t test/myapp .
+    Sending build context to Docker daemon 2.048 kB
+    Error response from daemon: Unknown instruction: RUNCMD
+
 The Docker daemon runs the instructions in the `Dockerfile` one-by-one,
 committing the result of each instruction
 to a new image if necessary, before finally outputting the ID of your