urlutil: add a `get_pull_paths` to perform the pull destination logic

As is this changeset does not change anything. However having an official empty
point will help unifying the logic and encapsulate the details and update the
logic to support path definition pointing to multiple other path.

Differential Revision: https://phab.mercurial-scm.org/D10378

mercurial/commands.py

@@ -5387,12 +5387,8 b' def pull(ui, repo, *sources, **opts):'
         hint = _(b'use hg pull followed by hg update DEST')
         raise error.InputError(msg, hint=hint)
 
-    if not sources:
-        sources = [b'default']
-    for source in sources:
-        source, branches = urlutil.parseurl(
-            ui.expandpath(source), opts.get(b'branch')
-        )
+    sources = urlutil.get_pull_paths(repo, ui, sources, opts.get(b'branch'))
+    for source, branches in sources:
         ui.status(_(b'pulling from %s\n') % urlutil.hidepassword(source))
         ui.flush()
         other = hg.peer(repo, opts, source)

mercurial/utils/urlutil.py

@@ -453,6 +453,15 b' def get_push_paths(repo, ui, dests):'
         yield ui.getpath(dest, default=(b'default-push', b'default'))
 
 
+def get_pull_paths(repo, ui, sources, default_branches=()):
+    """yields all the `(path, branch)` selected as pull source by `sources`"""
+    if not sources:
+        sources = [b'default']
+    for source in sources:
+        url = ui.expandpath(source)
+        yield parseurl(url, default_branches)
+
+
 def parseurl(path, branches=None):
     '''parse url#branch, returning (url, (branch, branches))'''
     u = url(path)