Bug 1270317 - Define a clone_upstream_url property; r=jlund

We currently have a "clone_by_revision" property that indicates to
perform a `hg clone -r`. We use it for cloning from Try.

Cloning single revisions undermines the benefits of clone bundles. So,
I'll be replacing "clone_by_revision" with a feature that clones from
another "upstream" repo then does a `hg pull -r` on the wanted revision.

This commit starts that work by introducing a "clone_upstream_url"
property. We define it on Try. It is currently unused.

MozReview-Commit-ID: Dohs8bCTUkB

--HG--
extra : rebase_source : 17b643f32747d494db04a2e80c4f94308b13618e

testing/mozharness/configs/builds/branch_specifics.py

@@ -194,6 +194,9 @@ config = {
         'repo_path': 'try',
         'clone_by_revision': True,
         'clone_with_purge': True,
+        # FUTURE this should be a unified repo because Try pushes may e.g.
+        # be on Aurora or Beta revisions.
+        'clone_upstream_url': 'https://hg.mozilla.org/mozilla-central',
         'tinderbox_build_dir': '%(who)s-%(got_revision)s',
         'to_tinderbox_dated': False,
         'include_post_upload_builddir': True,

testing/mozharness/configs/single_locale/try.py

@@ -25,6 +25,7 @@ config = {
         "repo": "https://hg.mozilla.org/try",
         "revision": "%(revision)s",
         "dest": "try",
+        "clone_upstream_url": "https://hg.mozilla.org/mozilla-central",
         "clone_by_revision": True,
         "clone_with_purge": True,
     }, {

testing/mozharness/mozharness/mozilla/building/buildbase.py

@@ -1166,6 +1166,7 @@ or run without that action (ie: --no-{action})"
 
         if c.get('clone_with_purge'):
             vcs_checkout_kwargs['clone_with_purge'] = True
+        vcs_checkout_kwargs['clone_upstream_url'] = c.get('clone_upstream_url')
         rev = self.vcs_checkout(**vcs_checkout_kwargs)
         if c.get('is_automation'):
             changes = self.buildbot_config['sourcestamp']['changes']