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>