doc: clone and outgoing point to pull for valid path docs

doc/hg.1.txt

@@ -155,6 +155,8 b' clone [options] <source> [dest]::'
     errors.  In these cases, use the --pull option to avoid
     hardlinking.
 
+    See pull for valid source format details.
+
     options:
     -U, --noupdate   do not update the new working directory
     --pull           use pull protocol to copy metadata
@@ -388,6 +390,8 b' outgoing [-p] [dest]::'
     default push repo. These are the changesets that would be pushed
     if a push was requested.
 
+    See pull for valid source format details.
+
     options:
     -p, --patch           show patch