Allow checkurl() to return True in case file is present but neither s…

…ize nor filename are known

From https://git-annex.branchable.com/design/external_special_remote_protocol/
The Size is the size in bytes, or use UNKNOWN if the size could not be determined.
The Filename can be empty (in which case a default is used), or can specify a filename that is suggested to be used for this url.

annexremote/annexremote.py

@@ -275,18 +275,13 @@ def checkurl(self, url):
             False if it can't currently be downloaded.
 
             In order to provide additional information, a list of dictionaries can be returned.
-            The dictionaries can have 3 keys: {'url': str, 'size': int, 'filename': str}
+            The dictionaries can have 3 keys: {'url': str, 'size': int, 'filename': str}. All of them are optional.
+            
             If there is only one file to be downloaded, we could return:
             [{'size': 512, 'filename':'example_file.txt'}]
-            Both `size` and `filename` can be ommited.
-
-            If there are multiple files to be downloaded from this url
-
 
-
-            The dictionaries are of the form:
+            Other examples:
             {'url':"https://example.com", 'size':512, 'filename':"example_file.txt"}
-
             [{'url':"Url1", 'size':512, 'filename':"Filename1"}, {'url':"Url2", 'filename':"Filename2"}]
 
 

docs/annexremote/annexremote.html

@@ -336,13 +336,12 @@ <h2 id="returns">Returns</h2>
 <p>True if the url's content can currently be downloaded and no additional information can be provided.
 False if it can't currently be downloaded.</p>
 <p>In order to provide additional information, a list of dictionaries can be returned.
-The dictionaries can have 3 keys: {'url': str, 'size': int, 'filename': str}
-If there is only one file to be downloaded, we could return:
-[{'size': 512, 'filename':'example_file.txt'}]
-Both <code>size</code> and <code>filename</code> can be ommited.</p>
-<p>If there are multiple files to be downloaded from this url</p>
-<p _filename_:_example_file.txt_="'filename':&quot;example_file.txt&quot;" _size_:512_="'size':512," _url_:_https:_example.com_="'url':&quot;https://example.com&quot;,">The dictionaries are of the form:</p>
-<p>[{'url':"Url1", 'size':512, 'filename':"Filename1"}, {'url':"Url2", 'filename':"Filename2"}]</p>
+The dictionaries can have 3 keys: {'url': str, 'size': int, 'filename': str}. All of them are optional.</p>
+<p>If there is only one file to be downloaded, we could return:
+[{'size': 512, 'filename':'example_file.txt'}]</p>
+<p>Other examples:
+{'url':"https://example.com", 'size':512, 'filename':"example_file.txt"}
+[{'url':"Url1", 'size':512, 'filename':"Filename1"}, {'url':"Url2", 'filename':"Filename2"}]</p>
 </dd>
 </dl></section>
 </dd>

tests/test_GitAnnexRequestMessages.py

@@ -164,6 +164,12 @@ def TestClaimurlFailure(self):
         self.annex.Listen(io.StringIO("CLAIMURL Url"))
         self.assertEqual(utils.second_buffer_line(self.output), "CLAIMURL-FAILURE")
 
+    def TestCheckurlContentsTrue(self):
+        self.remote.checkurl.return_value = True
+        self.annex.Listen(io.StringIO("CHECKURL Url"))
+        self.remote.checkurl.assert_called_once_with("Url")
+        self.assertEqual(utils.second_buffer_line(self.output), "CHECKURL-CONTENTS UNKNOWN")
+
     def TestCheckurlContents(self):
         self.remote.checkurl.return_value = [{'size':512,'filename':"Filename"}]
         self.annex.Listen(io.StringIO("CHECKURL Url"))