Don't remove comment from public key, and improve error message for duplicate keys (github_key) (#22282)

* improve error message for duplicate public keys

* don't consider self when searching for duplicates

* don't strip comment from key

lib/ansible/modules/source_control/github_key.py

@@ -132,12 +132,12 @@ class GitHubSession(object):
 
 def get_all_keys(session):
     url = API_BASE + '/user/keys'
+    result = []
     while url:
         r = session.request('GET', url)
-        for key in r.json():
-            yield key
-
+        result.extend(r.json())
         url = r.links().get('next')
+    return result
 
 
 def create_key(session, name, pubkey, check_mode):
@@ -176,11 +176,20 @@ def ensure_key_absent(session, name, check_mode):
             'deleted_keys': to_delete}
 
 
-def ensure_key_present(session, name, pubkey, force, check_mode):
-    matching_keys = [k for k in get_all_keys(session) if k['title'] == name]
+def ensure_key_present(module, session, name, pubkey, force, check_mode):
+    all_keys = get_all_keys(session)
+    matching_keys = [k for k in all_keys if k['title'] == name]
     deleted_keys = []
 
-    if matching_keys and force and matching_keys[0]['key'] != pubkey:
+    new_signature = pubkey.split(' ')[1]
+    for key in all_keys:
+        existing_signature = key['key'].split(' ')[1]
+        if new_signature == existing_signature and key['title'] != name:
+            module.fail_json(msg=(
+                "another key with the same content is already registered "
+                "under the name |{}|").format(key['title']))
+
+    if matching_keys and force and matching_keys[0]['key'].split(' ')[1] != new_signature:
         delete_keys(session, matching_keys, check_mode=check_mode)
         (deleted_keys, matching_keys) = (matching_keys, [])
 
@@ -221,15 +230,12 @@ def main():
         # Keys consist of a protocol, the key data, and an optional comment.
         if len(pubkey_parts) < 2:
             module.fail_json(msg='"pubkey" parameter has an invalid format')
-
-        # Strip out comment so we can compare to the keys GitHub returns.
-        pubkey = ' '.join(pubkey_parts[:2])
     elif state == 'present':
         module.fail_json(msg='"pubkey" is required when state=present')
 
     session = GitHubSession(module, token)
     if state == 'present':
-        result = ensure_key_present(session, name, pubkey, force=force,
+        result = ensure_key_present(module, session, name, pubkey, force=force,
                                     check_mode=module.check_mode)
     elif state == 'absent':
         result = ensure_key_absent(session, name, check_mode=module.check_mode)