outgoing: use `get_push_paths` in the revset too

The revsets now use the same code as everyone and is ready for entry in
`[paths]` pointing to multiple entries.

Differential Revision: https://phab.mercurial-scm.org/D10393

mercurial/revset.py

@@ -1855,15 +1855,13 b' def outgoing(repo, subset, x):'
     dest = (
         l and getstring(l[0], _(b"outgoing requires a repository path")) or b''
     )
-    if not dest:
+    if dest:
         # ui.getpath() explicitly tests for None, not just a boolean
-        dest = None
-    path = repo.ui.getpath(dest, default=(b'default-push', b'default'))
-    if not path:
-        raise error.Abort(
-            _(b'default repository not configured!'),
-            hint=_(b"see 'hg help config.paths'"),
-        )
+        dests = [dest]
+    else:
+        dests = []
+    missing = set()
+    for path in urlutil.get_push_paths(repo, repo.ui, dests):
     dest = path.pushloc or path.loc
     branches = path.branch, []
 
@@ -1877,8 +1875,9 b' def outgoing(repo, subset, x):'
         repo.ui.popbuffer()
     finally:
         other.close()
+        missing.update(outgoing.missing)
     cl = repo.changelog
-    o = {cl.rev(r) for r in outgoing.missing}
+    o = {cl.rev(r) for r in missing}
     return subset & o