/changes/: Return more data

Allow more data to be provided in the JSON results from /changes/,
including all revisions of the change (aka patch sets), commit
message data, files, and URLs to fetch the revisions with.

Revisions are indexed by the commit SHA-1, as a commit can only
really appear once per change. The current_revision field points
to the revision structure that is the most recent for this change.

Within a revision structure the fetch map provides a set of URLs and
the corresponding reference that should point to the commit. This can
be used to fetch the change over the Git protocols. All available URL
permutations are made by the server rather than the client, giving the
server more flexibility in the long term to move changes around. This
should one day support moving closed changes out to archive
repositories with different reference names.

$ curl 'http://127.0.0.1:8080/changes/?q=97&format=JSON&o=CURRENT_REVISION&o=CURRENT_COMMIT&o=CURRENT_FILES'
)]}'
[
  {
    "project": "gerrit",
    "branch": "master",
    "id": "I7ea46d2e2ee5c64c0d807677859cfb7d90b8966a",
    "subject": "Use an EventBus to manage star icons",
    "status": "NEW",
    "created": "2012-04-25 00:52:25.580000000",
    "updated": "2012-04-25 00:52:25.586000000",
    "_sortkey": "001c9bf400000061",
    "_number": 97,
    "owner": {
      "name": "Shawn Pearce"
    },
    "current_revision": "184ebe53805e102605d11f6b143486d15c23a09c",
    "revisions": {
      "184ebe53805e102605d11f6b143486d15c23a09c": {
        "_number": 1,
        "fetch": {
          "git": {
            "url": "git://localhost/gerrit",
            "ref": "refs/changes/97/97/1"
          },
          "http": {
            "url": "http://127.0.0.1:8080/gerrit",
            "ref": "refs/changes/97/97/1"
          }
        },
        "commit": {
          "parents": [
            {
              "commit": "1eee2c9d8f352483781e772f35dc586a69ff5646",
              "subject": "Migrate contributor agreements to All-Projects."
            }
          ],
          "author": {
            "name": "Shawn O. Pearce",
            "email": "sop@google.com",
            "date": "2012-04-24 18:08:08.000000000",
            "tz": -420
          },
          "committer": {
            "name": "Shawn O. Pearce",
            "email": "sop@google.com",
            "date": "2012-04-24 18:08:08.000000000",
            "tz": -420
          },
          "subject": "Use an EventBus to manage star icons",
          "message": "Use an EventBus to manage star icons\n\nImage widgets that need to ..."
        },
        "files": {
          "gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeCache.java": {
            "lines_deleted": 8
          },
          "gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeDetailCache.java": {
            "lines_inserted": 1
          },
          "gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeScreen.java": {
            "lines_inserted": 11,
            "lines_deleted": 19
          },
          "gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeTable.java": {
            "lines_inserted": 23,
            "lines_deleted": 20
          },
          "gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/StarCache.java": {
            "status": "D",
            "lines_deleted": 139
          },
          "gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/StarredChanges.java": {
            "status": "A",
            "lines_inserted": 204
          },
          "gerrit-gwtui/src/main/java/com/google/gerrit/client/ui/Screen.java": {
            "lines_deleted": 9
          }
        }
      }
    }
  }
]

Change-Id: I9589cc46b3dfcc43e799fdd40ee8d6c292c4f17b

gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/Patch.java

@@ -82,7 +82,10 @@ public final class Patch {
     RENAMED('R'),
 
     /** Path was copied from {@link Patch#getSourceFileName()}. */
-    COPIED('C');
+    COPIED('C'),
+
+    /** Sufficient amount of content changed to claim the file was written. */
+    REWRITE('W');
 
     private final char code;