add docs for commit --change

Docker-DCO-1.1-Signed-off-by: Daniel, Dao Quang Minh <dqminh89@gmail.com> (github: dqminh)

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)

docs/man/docker-commit.1.md

@@ -8,6 +8,7 @@ docker-commit - Create a new image from a container's changes
 **docker commit**
 [**-a**|**--author**[=*AUTHOR*]]
 [**--help**]
+[**-c**|**--change**[= []**]]
 [**-m**|**--message**[=*MESSAGE*]]
 [**-p**|**--pause**[=*true*]]
 CONTAINER [REPOSITORY[:TAG]]
@@ -19,6 +20,9 @@ Using an existing container's name or ID you can create a new image.
 **-a**, **--author**=""
    Author (e.g., "John Hannibal Smith <hannibal@a-team.com>")
 
+**-c** , **--change**=[]
+   Apply a modification in Dockerfile format before committing the image.
+
 **--help**
   Print usage statement
 
@@ -38,8 +42,17 @@ create a new image run docker ps to find the container's ID and then run:
     # docker commit -m="Added Apache to Fedora base image" \
       -a="A D Ministrator" 98bd7fc99854 fedora/fedora_httpd:20
 
+## Modify configuration settings before committing the image
+An existing container was created without the necessary environment variable
+DEBUG set to "true". To create a new image based on the container with a
+correct DEBUG environment variable, run docker ps to find the container's ID
+and then run
+
+    # docker commit -c="ENV DEBUG true" 98bd7fc99854 debug-image
+
 # HISTORY
 April 2014, Originally compiled by William Henry (whenry at redhat dot com)
 based on docker.com source material and in
 June 2014, updated by Sven Dowideit <SvenDowideit@home.org.au>
 July 2014, updated by Sven Dowideit <SvenDowideit@home.org.au>
+Oct 2014, updated by Daniel, Dao Quang Minh <daniel at nitrous dot io>

docs/sources/reference/commandline/cli.md

@@ -694,6 +694,7 @@ you refer to it on the command line.
     Create a new image from a container's changes
 
       -a, --author=""     Author (e.g., "John Hannibal Smith <hannibal@a-team.com>")
+      -c, --change=[]     Apply a modification in Dockerfile format before committing the image
       -m, --message=""    Commit message
       -p, --pause=true    Pause container during commit
 
@@ -720,6 +721,19 @@ If this behavior is undesired, set the 'p' option to false.
     REPOSITORY                        TAG                 ID                  CREATED             VIRTUAL SIZE
     SvenDowideit/testimage            version3            f5283438590d        16 seconds ago      335.7 MB
 
+#### Commit an existing container with new configurations
+
+    $ sudo docker ps
+    ID                  IMAGE               COMMAND             CREATED             STATUS              PORTS
+    c3f279d17e0a        ubuntu:12.04        /bin/bash           7 days ago          Up 25 hours
+    197387f1b436        ubuntu:12.04        /bin/bash           7 days ago          Up 25 hours
+    $ sudo docker inspect -f "{{ .Config.Env }}" c3f279d17e0a
+    [HOME=/ PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin]
+    $ sudo docker commit --change "ENV DEBUG true" c3f279d17e0a  SvenDowideit/testimage:version3
+    f5283438590d
+    $ sudo docker inspect -f "{{ .Config.Env }}" f5283438590d
+    [HOME=/ PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin DEBUG=true]
+
 ## cp
 
 Copy files/folders from a container's filesystem to the host