phabricator: avoid calling differential.getcommitmessage

Previously, we call differential.getcommitmessage API to get commit
messages. Now we read that from "Differential Revision" object fetched
via "differential.query" API.

This removes one API call per patch.

contrib/phabricator.py

@@ -307,8 +307,6 b' def phabsend(ui, repo, *revs, **opts):'
                                             ctx.description().split('\n')[0]))
         lastrevid = newrevid
 
-_summaryre = re.compile('^Summary:\s*', re.M)
-
 # Map from "hg:meta" keys to header understood by "hg import". The order is
 # consistent with "hg export" output.
 _metanamemap = util.sortdict([(r'user', 'User'), (r'date', 'Date'),
@@ -377,6 +375,20 b' def querydrev(repo, params, stack=False)'
     result.reverse()
     return result
 
+def getdescfromdrev(drev):
+    """get description (commit message) from "Differential Revision"
+
+    This is similar to differential.getcommitmessage API. But we only care
+    about limited fields: title, summary, test plan, and URL.
+    """
+    title = drev[r'title']
+    summary = drev[r'summary'].rstrip()
+    testplan = drev[r'testPlan'].rstrip()
+    if testplan:
+        testplan = 'Test Plan:\n%s' % testplan
+    uri = 'Differential Revision: %s' % drev[r'uri']
+    return '\n\n'.join(filter(None, [title, summary, testplan, uri]))
+
 def readpatch(repo, params, write, stack=False):
     """generate plain-text patch readable by 'hg import'
 
@@ -396,13 +408,9 b' def readpatch(repo, params, write, stack'
 
         diffid = max(int(v) for v in drev[r'diffs'])
         body = callconduit(repo, 'differential.getrawdiff', {'diffID': diffid})
-        desc = callconduit(repo, 'differential.getcommitmessage',
-                           {'revision_id': drev[r'id']})
+        desc = getdescfromdrev(drev)
         header = '# HG changeset patch\n'
 
-        # Remove potential empty "Summary:"
-        desc = _summaryre.sub('', desc)
-
         # Try to preserve metadata from hg:meta property. Write hg patch
         # headers that can be read by the "import" command. See patchheadermap
         # and extract in mercurial/patch.py for supported headers.