docs: auto generate pouch cli/api docs via code

docs/api/HTTP_API.md

@@ -1239,8 +1239,40 @@ json :
 ```
 
 
+<a name="imagehistory"></a>
+### Get an image's history
+```
+GET /images/{imageid}/history
+```
+
+
+#### Description
+Return the history of each layer of image
+
+
+#### Parameters
+
+|Type|Name|Description|Schema|
+|---|---|---|---|
+|**Path**|**imageid**  <br>*required*|Image name or id|string|
+
+
+#### Responses
+
+|HTTP Code|Description|Schema|
+|---|---|---|
+|**200**|no error|< [HistoryResultItem](#historyresultitem) > array|
+|**404**|An unexpected 404 error occurred.|[Error](#error)|
+|**500**|An unexpected server error occurred.|[Error](#error)|
+
+
+#### Produces
+
+* `application/json`
+
+
 <a name="imageinspect"></a>
-### Inspect a image
+### Inspect an image
 ```
 GET /images/{imageid}/json
 ```
@@ -2299,6 +2331,22 @@ Information about a container's graph driver.
 |**Name**  <br>*required*|string|
 
 
+<a name="historyresultitem"></a>
+### HistoryResultItem
+An object containing image history at API side.
+
+
+|Name|Description|Schema|
+|---|---|---|
+|**Author**  <br>*required*|the author of the build point.|string|
+|**Comment**  <br>*required*|a custom message set when creating the layer.|string|
+|**Created**  <br>*required*|the combined date and time at which the layer was created.|integer (int64)|
+|**CreatedBy**  <br>*required*|the command which created the layer.|string|
+|**EmptyLayer**  <br>*required*|mark whether the history item created a filesystem diff or not.|boolean|
+|**ID**  <br>*required*|ID of each layer image.|string|
+|**Size**  <br>*required*|size of each layer image.|integer (int64)|
+
+
 <a name="hostconfig"></a>
 ### HostConfig
 Container configuration that depends on the host we are running on

docs/commandline/pouch.md

@@ -25,6 +25,7 @@ pouch is a client side tool pouch to interact with daemon side process pouchd. F
 * [pouch events](pouch_events.md)	 - Get real time events from the daemon
 * [pouch exec](pouch_exec.md)	 - Exec a process in a running container
 * [pouch gen-doc](pouch_gen-doc.md)	 - Generate docs
+* [pouch history](pouch_history.md)	 - Display history information on image
 * [pouch image](pouch_image.md)	 - Manage image
 * [pouch images](pouch_images.md)	 - List all images
 * [pouch info](pouch_info.md)	 - Display system-wide information

docs/commandline/pouch_history.md

@@ -0,0 +1,45 @@
+## pouch history
+
+Display history information on image
+
+### Synopsis
+
+Return the history information about image
+
+```
+pouch history [OPTIONS] IMAGE
+```
+
+### Examples
+
+```
+pouch history busybox:latest
+IMAGE          CREATED      CREATED BY                                      SIZE        COMMENT
+e1ddd7948a1c   1 week ago   /bin/sh -c #(nop)  CMD ["sh"]                   0.00 B
+<missing>      1 week ago   /bin/sh -c #(nop) ADD file:96fda64a6b725d4...   716.06 KB  
+```
+
+### Options
+
+```
+  -h, --help       help for history
+      --human      Print information in human readable format (default true)
+      --no-trunc   Do not truncate output
+  -q, --quiet      Only show image numeric ID
+```
+
+### Options inherited from parent commands
+
+```
+  -D, --debug              Switch client log level to DEBUG mode
+  -H, --host string        Specify connecting address of Pouch CLI (default "unix:///var/run/pouchd.sock")
+      --tlscacert string   Specify CA file of TLS
+      --tlscert string     Specify cert file of TLS
+      --tlskey string      Specify key file of TLS
+      --tlsverify          Use TLS and verify remote
+```
+
+### SEE ALSO
+
+* [pouch](pouch.md)	 - An efficient container engine
+