Update Makefile and Add Testing Info

Update the Makefile to allow users to build the
image with their changes using podman.
Update the Readme to add instructions on how to
test changes.

Signed-off-by: Urvashi <[email protected]>

Author: umohnani8

Makefile

@@ -9,6 +9,20 @@ include $(addprefix ./vendor/github.com/openshift/build-machinery-go/make/, \
 
 IMAGE_REGISTRY :=registry.ci.openshift.org
 
+# Check which builder to use - default is imagebuilder
+ifeq ($(BUILDER), podman)
+# Use podman to build the must gather image
+# Please ensure you have podman installed on your machine for this
+IMAGE_BUILD_BUILDER := podman build
+# Clear all build default flags
+IMAGE_BUILD_DEFAULT_FLAGS :=
+# Set authfile if the user passes another location for the authentication file
+ifneq ($(strip $(AUTH_FILE)),)
+IMAGE_BUILD_DEFAULT_FLAGS := --authfile=$(AUTH_FILE)
+endif
+endif
+
+
 # This will call a macro called "build-image" which will generate image specific targets based on the parameters:
 # $0 - macro name
 # $1 - target name

README.md

@@ -15,5 +15,23 @@ included.
 You can run `must-gather` on a cluster with `oc adm must-gather`. 
 Use `-h` flag to see available options.
 
+## How to test
+Build a new must-gather image with your changes using the Makefile. There are two options in the Makefile, `make` will use imagebuilder to build the image while `make BUILDER=podman` will use podman to build the image.
+
+If using `make BUILDER=podman`, please set the `AUTH_FILE` parameter pointing to an authentication file that has credentials for the `registry.ci.openshift.org` registry. Ensure that you are connected to the VPN before building the image.
+```
+make BUILDER=podman AUTH_FILE=/path/to/authfile
+```
+
+Once the image is built, push it to a registry where it can be accessed from. 
+```
+podman push [built-image] [registry/username/your-built-image]
+``` 
+
+To test your new changes with a cluster, run the following:
+```
+oc adm must-gather --image=registry/username/your-built-image
+```
+
 ## Obfuscate confidential information
 There is a dedicated effort to obfuscate and omit confidential information. Head over to [openshift/must-gather-clean](https://github.com/openshift/must-gather-clean) for more information.