Merge pull request #6803 from vieux/pr_6176

Implement tail for docker logs
Upstream-commit: 49d49ac98f06d0016bcbda56f3ef158c64167bae
Component: engine

components/engine/docs/sources/reference/api/docker_remote_api_v1.13.md

@@ -306,7 +306,7 @@ Get stdout and stderr logs from the container ``id``
 
     **Example request**:
 
-       GET /containers/4fa6e0f0c678/logs?stderr=1&stdout=1&timestamps=1&follow=1 HTTP/1.1
+       GET /containers/4fa6e0f0c678/logs?stderr=1&stdout=1&timestamps=1&follow=1&tail=10 HTTP/1.1
 
     **Example response**:
 
@@ -319,14 +319,12 @@ Get stdout and stderr logs from the container ``id``
 
      
 
-    -   **follow** – 1/True/true or 0/False/false, return stream.
-        Default false
-    -   **stdout** – 1/True/true or 0/False/false, if logs=true, return
-        stdout log. Default false
-    -   **stderr** – 1/True/true or 0/False/false, if logs=true, return
-        stderr log. Default false
-    -   **timestamps** – 1/True/true or 0/False/false, if logs=true, print
-        timestamps for every log line. Default false
+    -   **follow** – 1/True/true or 0/False/false, return stream. Default false
+    -   **stdout** – 1/True/true or 0/False/false, show stdout log. Default false
+    -   **stderr** – 1/True/true or 0/False/false, show stderr log. Default false
+    -   **timestamps** – 1/True/true or 0/False/false, print timestamps for
+        every log line. Default false
+    -   **tail** – Output specified number of lines at the end of logs: `all` or `<number>`. Default all
 
     Status Codes:
 

components/engine/docs/sources/reference/commandline/cli.md

@@ -738,13 +738,15 @@ specify this by adding the server name.
 
       -f, --follow=false        Follow log output
       -t, --timestamps=false    Show timestamps
+      --tail="all"              Output the specified number of lines at the end of logs (defaults to all logs)
 
-The `docker logs` command batch-retrieves all logs
-present at the time of execution.
+The `docker logs` command batch-retrieves logs present at the time of execution.
 
-The ``docker logs --follow`` command will first return all logs from the
-beginning and then continue streaming new output from the container's `STDOUT`
-and `STDERR`.
+The `docker logs --follow` command will continue streaming the new output from
+the container's `STDOUT` and `STDERR`.
+
+Passing a negative number or a non-integer to `--tail` is invalid and the
+value is set to `all` in that case. This behavior may change in the future.
 
 ## port