docs: clarify that --karg can be passed multiple times

It is not clear from the current man-page that `--karg` can be
passed multiple times. From reading the code it seems to be the
case but because it's not obvious (to me) I also added a small
testcase to the CI to ensure that I'm not misreading things.

I added a small comment to the docs that it can be given
multiple times.

.github/workflows/ci.yml

@@ -135,9 +135,10 @@ jobs:
           echo 'ssh-ed25519 ABC0123 testcase@example.com' > test_authorized_keys
           sudo podman run --rm -ti --privileged -v ./test_authorized_keys:/test_authorized_keys --env RUST_LOG=debug -v /:/target -v /var/lib/containers:/var/lib/containers -v ./usr/bin/bootc:/usr/bin/bootc --pid=host --security-opt label=disable \
             quay.io/centos-bootc/centos-bootc-dev:stream9 bootc install to-filesystem \
-            --karg=foo=bar --disable-selinux --replace=alongside --root-ssh-authorized-keys=/test_authorized_keys /target
+            --karg=foo=bar --karg=baz=foobar --disable-selinux --replace=alongside --root-ssh-authorized-keys=/test_authorized_keys /target
           ls -al /boot/loader/
           sudo grep foo=bar /boot/loader/entries/*.conf
+          sudo grep baz=foobar /boot/loader/entries/*.conf
           grep authorized_keys /ostree/deploy/default/deploy/*/etc/tmpfiles.d/bootc-root-ssh.conf
           # TODO fix https://github.com/containers/bootc/pull/137
           sudo chattr -i /ostree/deploy/default/deploy/*

docs/src/man/bootc-install-to-disk.md

@@ -96,7 +96,7 @@ disabled but where the target does have SELinux enabled.
 
 **\--karg**=*KARG*
 
-:   Add a kernel argument
+:   Add a kernel argument (can be given multiple times)
 
 **\--root-ssh-authorized-keys**=*ROOT_SSH_AUTHORIZED_KEYS*
 

docs/src/man/bootc-install-to-filesystem.md

@@ -98,7 +98,7 @@ disabled but where the target does have SELinux enabled.
 
 **\--karg**=*KARG*
 
-:   Add a kernel argument
+:   Add a kernel argument (can be given multiple times)
 
 **\--root-ssh-authorized-keys**=*ROOT_SSH_AUTHORIZED_KEYS*