phabricator: extract the logic to amend diff properties to a function

This will be needed on a separate code path when dealing with folding revisions.
And since we know that will involve adding multiple local commmits to the diff
properties instead of just one, restructure the logic slightly to allow it.

Differential Revision: https://phab.mercurial-scm.org/D8312

hgext/phabricator.py

@@ -1168,6 +1168,20 b' def userphids(ui, names):'
     return [entry[b'phid'] for entry in data]
 
 
+def _amend_diff_properties(unfi, drevid, newnodes, diff):
+    """update the local commit list for the ``diff`` associated with ``drevid``
+
+    This is a utility function for the amend phase of ``phabsend``, which
+    converts failures to warning messages.
+    """
+    try:
+        writediffproperties([unfi[newnode] for newnode in newnodes], diff)
+    except util.urlerr.urlerror:
+        # If it fails just warn and keep going, otherwise the DREV
+        # associations will be lost
+        unfi.ui.warnnoi18n(b'Failed to update metadata for D%d\n' % drevid)
+
+
 @vcrcommand(
     b'phabsend',
     [
@@ -1357,17 +1371,10 b' def phabsend(ui, repo, *revs, **opts):'
                     newnode = new.commit()
 
                     mapping[old.node()] = [newnode]
-                    # Update diff property
-                    # If it fails just warn and keep going, otherwise the DREV
-                    # associations will be lost
-                    try:
-                        writediffproperties(
-                            [unfi[newnode]], diffmap[old.node()]
-                        )
-                    except util.urlerr.urlerror:
-                        ui.warnnoi18n(
-                            b'Failed to update metadata for D%d\n' % drevid
-                        )
+
+                    _amend_diff_properties(
+                        unfi, drevid, [newnode], diffmap[old.node()]
+                    )
                 # Remove local tags since it's no longer necessary
                 tagname = b'D%d' % drevid
                 if tagname in repo.tags():