urlutil: add a new `get_unique_push_path` This function is dedicated to call that needs a single destination. Currently most caller actually need that since few actually support multiple destinations (the most importants `hg push` and `hg outgoing` do). So having a clear API point for that will be important when the time comes to have a single `[paths]` alias resolving to multiple urls. Differential Revision: https://phab.mercurial-scm.org/D10407

fetch: use `get_unique_pull_path` to retrieve the path The fetch command does not support multiple destination, so we use the new dedicated API for that. Differential Revision: https://phab.mercurial-scm.org/D10406

patchbomb: use `get_unique_pull_path` The patchbomb code does not support multiple destinations yet. It would not be too hard to implemented since `hg outgoing` does. However that is a bit too much of a detour right now. In addition that kind of "select outgoing changesets for processing" code exist for various commands so the best would be to factor it out later. Let us use the dedicated API until this is solved. This comes with a small output change in the test that I find more accurate. So I kept it. Differential Revision: https://phab.mercurial-scm.org/D10405

narrow: use `get_unique_pull_path` The narrow's `tracked` command does not support multiple destination, lets use the dedicated API then. Differential Revision: https://phab.mercurial-scm.org/D10404

urlutil: add a new `get_unique_pull_path` This function is dedicated to call that needs a single destination. Currently most caller actually need that since few actually support multiple destinations (the most importants `hg push` and `hg outgoing` do). So having a clear API point for that will be important when the time comes to have a single `[paths]` alias resolving to multiple urls. Differential Revision: https://phab.mercurial-scm.org/D10403

mq: use the new `get_clone_path` to get the remote url We stop using `ui.expandpath` to use a function with a more defined semantic. This will help us to make it an option to point [paths] entry to multiple destination. Differential Revision: https://phab.mercurial-scm.org/D10402

urlutil: add a `get_clone_path` function We add a new function with a semantic focussed on `clone` operation (so without an existing repository). I am not certain the return type is the best, but this is what we need for now. Once all caller are migrated we might start thinking about that the API should be. For now that will do. Differential Revision: https://phab.mercurial-scm.org/D10401

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

incoming: use `urlutil.get_pull_paths` Lets use the new method to increase code reuse. However I did not implement support for multiple source yet. It would be possible create multiple temporary bundle, but that is a bit too much work outside of my current route to make the detour. Differential Revision: https://phab.mercurial-scm.org/D10392

outgoing: accept multiple destinations This align the behavior of `hg outgoing` with the one of `hg incoming`. In addition this prepare the introduction of having simple `path` resolve to multiple destination in practice (eg: `default`) Differential Revision: https://phab.mercurial-scm.org/D10391