Add support for external container

External containers are containers created outside of Podman.
For example Buildah and CRI-O Containers.

$ buildah from alpine
alpine-working-container
$ buildah run alpine-working-container touch /test
$ podman container exists --external alpine-working-container

$ podman container diff alpine-working-container
C /etc
A /test

Added --external flag to refer to external containers, rather then --storage.

Added --external for podman container exists and modified podman ps to use
--external rather then --storage.  It was felt that --storage would confuse
the user into thinking about changing the storage driver or options.

--storage is still supported through the use of aliases.

Finally podman contianer diff, does not require the --external flag, since it
there is little change of users making the mistake, and would just be a pain
for the user to remember the flag.

podman container exists --external is required because it could fool scripts
that rely on the existance of a Podman container, and there is a potential
for a partial deletion of a container, which could mess up existing users.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/docs/source/markdown/podman-container-exists.1.md b/docs/source/markdown/podman-container-exists.1.md
index b8be07cb9..3d151cfce 100644
--- a/docs/source/markdown/podman-container-exists.1.md
+++ b/docs/source/markdown/podman-container-exists.1.md
@@ -4,7 +4,7 @@
 podman-container-exists - Check if a container exists in local storage
 
 ## SYNOPSIS
-**podman container exists** *container*
+**podman container exists** [*options*] *container*
 
 ## DESCRIPTION
 **podman container exists** checks if a container exists in local storage. The **ID** or **Name**
@@ -14,6 +14,9 @@ was an issue accessing the local storage.
 
 ## OPTIONS
 
+**--external**=*true|false*
+Check for external containers as well as Podman containers. These external containers are generally created via other container technology such as Buildah or CRI-O.
+
 **-h**, **--help**
 Print usage statement
 
@@ -33,6 +36,13 @@ $ echo $?
 1
 ```
 
+Check if an container called `ubi8-working-container` created via Buildah exists in local storage (the container does not actually exist).
+```
+$ podman container exists --external ubi8-working-container
+$ echo $?
+1
+```
+
 ## SEE ALSO
 podman(1)