Bug 1554987 - Invoke git push with a remote name for mach try. r=ahal

The git version shipped in some versions of OSX is patched by apple in a
way such that doing `git push hg::ssh://...` fails with an error message
like `Invalid remote name "hg::ssh://...`.

So instead, we define a named remote via inline configuration, and use
that remote's name for the push.

Differential Revision: https://phabricator.services.mozilla.com/D35351

--HG--
extra : moz-landing-system : lando

python/mozversioncontrol/mozversioncontrol/__init__.py

@@ -456,7 +456,11 @@ class GitRepository(Repository):
 
         self._run('commit', '--allow-empty', '-m', message)
         try:
-            subprocess.check_call((self._tool, 'push', 'hg::ssh://hg.mozilla.org/try',
+            subprocess.check_call((self._tool,
+                                   '-c',
+                                   'remote.try.url=hg::ssh://hg.mozilla.org/try',
+                                   'push',
+                                   'try',
                                    '+HEAD:refs/heads/branches/default/tip'), cwd=self.path)
         finally:
             self._run('reset', 'HEAD~')