[doc][rerun.sh] Add some exception.

doc/index.rst

@@ -241,8 +241,10 @@ On CI platform usually some variables are available for the convenience. Since a
 Still, you may want to pass some other vars. `DOCKER_RUN_OPTS='-e MY_VARIABLE_VALUE'` should do the trick.
 You can even set it to a specific value: `DOCKER_RUN_OPTS='-e MY_VARIABLE_VALUE=42'` (format varies per CI platform. These are Gitlab CI example).
 
-(Experimental) Re-use the container image
-------------------------------------------------
+Re-use the container image
+--------------------------
+
+NOTE: This is still experimental.
 
 ``industrial_ci`` builds a ``Docker`` image using the associated repository on the specified operating system per every job. While the built Docker container is thrown away once the job finishes by default, there's a way to access the built image post job so that you can re-use it.
 
@@ -682,7 +684,7 @@ Recurring runs for debugging
 Please note that `run_ci` and `run_travis` will download all dependencies every time, just as CI services would do.
 For recurring runs, e.g. in a debugging session, this might not be desired.
 
-As an alternative `rerun_ci` could be used. It take the same argument as `run_ci`, but will run the build incrementally and only download or compile after changes.
+As an alternative `rerun_ci` could be used. It take the same argument as `run_ci` (note for `some limitations <#note-for-rerun-ci-limitations>`_), but will run the build incrementally and only download or compile after changes.
 
 This results in much faster execution for recurring runs, but has some disadvantages as well:
 
@@ -706,6 +708,11 @@ The cached images can be listed with
 
   $ rosrun industrial_ci rerun_ci --list
 
+Note for rerun_ci limitations
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+`rerun_ci` is managing `DOCKER_COMMIT` and `DOCKER_COMMIT_MSG` variables under the hood, so if the user set them they will not take effect, unlike `normal cases <#re-use-the-container-image>`_.
+
 For maintainers of industrial_ci repository
 ================================================