gerrit/api.py: Add get_revision() helper.

Allows easily getting at more than just the commit message.
I intend to look at the author to whitelist bots from binary size
checks (initially).

Bug: 702625
Change-Id: I684fdfacc88635ec4849216c74183f63f9d54810
Reviewed-on: https://chromium-review.googlesource.com/1070483
Commit-Queue: agrieve <agrieve@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>

recipes/README.recipes.md

@@ -345,7 +345,7 @@ Args:
 Returns:
   the name of the branch
 
-— **def [get\_changes](/recipes/recipe_modules/gerrit/api.py#135)(self, host, query_params, start=None, limit=None, o_params=None, step_test_data=None, \*\*kwargs):**
+— **def [get\_changes](/recipes/recipe_modules/gerrit/api.py#151)(self, host, query_params, start=None, limit=None, o_params=None, step_test_data=None, \*\*kwargs):**
 
 Query changes for the given host.
 
@@ -369,6 +369,19 @@ Get a branch from given project and commit
 
 Returns:
   the revision of the branch
+
+— **def [get\_revision\_info](/recipes/recipe_modules/gerrit/api.py#121)(self, host, change, patchset):**
+
+Returns the info for a given patchset of a given change.
+
+Args:
+  host: Gerrit host to query.
+  change: The change number.
+  patchset: The patchset number.
+
+Returns:
+  A dict for the target revision as documented here:
+      https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#list-changes
 ### *recipe_modules* / [git](/recipes/recipe_modules/git)
 
 [DEPS](/recipes/recipe_modules/git/__init__.py#1): [infra\_paths](#recipe_modules-infra_paths), [recipe\_engine/context][recipe_engine/recipe_modules/context], [recipe\_engine/path][recipe_engine/recipe_modules/path], [recipe\_engine/platform][recipe_engine/recipe_modules/platform], [recipe\_engine/properties][recipe_engine/recipe_modules/properties], [recipe\_engine/python][recipe_engine/recipe_modules/python], [recipe\_engine/raw\_io][recipe_engine/recipe_modules/raw_io], [recipe\_engine/step][recipe_engine/recipe_modules/step]

recipes/recipe_modules/gerrit/api.py

@@ -115,6 +115,22 @@ class GerritApi(recipe_api.RecipeApi):
     Returns:
       The description corresponding to given CL and patchset.
     """
+    ri = self.get_revision_info(host, change, patchset)
+    return ri['commit']['message']
+
+  def get_revision_info(self, host, change, patchset):
+    """
+    Returns the info for a given patchset of a given change.
+
+    Args:
+      host: Gerrit host to query.
+      change: The change number.
+      patchset: The patchset number.
+
+    Returns:
+      A dict for the target revision as documented here:
+          https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#list-changes
+    """
     assert int(change), change
     assert int(patchset), patchset
     cls = self.get_changes(
@@ -126,7 +142,7 @@ class GerritApi(recipe_api.RecipeApi):
     for ri in cl['revisions'].itervalues():
       # TODO(tandrii): add support for patchset=='current'.
       if str(ri['_number']) == str(patchset):
-        return ri['commit']['message']
+        return ri
 
     raise self.m.step.InfraFailure(
         'Error querying for CL description: host:%r change:%r; patchset:%r' % (