Add stat to ToCommit function for speed (#21337)

Calls to ToCommit are very slow due to fetching diffs, analyzing files.
This patch lets us supply `stat` as false to speed fetching a commit
when we don't need the diff.

/v1/repo/commits has a default `stat` set as true now. Set to false to
experience fetching thousands of commits per second instead of 2-5 per
second.

templates/swagger/v1_json.tmpl

@@ -3264,6 +3264,12 @@
             "name": "path",
             "in": "query"
           },
+          {
+            "type": "boolean",
+            "description": "include diff stats for every commit (disable for speedup, default 'true')",
+            "name": "stat",
+            "in": "query"
+          },
           {
             "type": "integer",
             "description": "page number of results to return (1-based)",