Merge branch 'laurent.heirendt-develop-patch-98215' into 'develop'

add instruction to detect host keys

See merge request R3/howto-cards!258

external/contribute/mirror-fork/mirror-fork.md

@@ -15,8 +15,9 @@ you should follow the follow simple steps.
 2. Expand the section on `Mirroring repositories`
 3. In the field `Git repository URL`, enter the SSH clone address from the main repository. In case of this repository, the address is `ssh://git@gitlab.lcsb.uni.lu:8022/R3/howto-cards.git`
 4. Select `Mirror Direction` as `Pull`
-5. `Authentication method` should be selected as `SSH public key`
-6. Then, click on the blue button `Mirror repository`
+5. Click on `Detect Host Keys`
+6. `Authentication method` should be selected as `SSH public key`
+7. Then, click on the blue button `Mirror repository`
 
 You will see an entry in the table below the blue button. Often, there is an error appearing. Now, in order to be able to perform the mirror, you need to set the SSH key.