Migrate project watches to git (part 1)

In git the project watch configuration of a user is stored in a
'watch.config' file in the refs/users/<sharded-id> user branch in the
All-Users repository.

The 'watch.config' file is a git config file that has one 'project'
section for all project watches of a project. This means if we ever
want to watch other entities we can add further sections in this file
(e.g. 'group' sections if we want to support watching of group
modifications).

The project name is used as subsection name and the filters with the
notify types that decide for which events email notifications should
be sent are represented as 'notify' values in the subsection. A
'notify' value is formatted as
"<filter> [<comma-separated-list-of-notify-types>]":

  [project "foo"]
    notify = * [ALL_COMMENTS]
    notify = branch:master [ALL_COMMENTS, NEW_PATCHSETS]
    notify = branch:master owner:self [SUBMITTED_CHANGES]

For a change event a notification will be send if any 'notify' value
of the corresponding project has both, a filter that matches the
change and a notify type that matches the event.

If two notify values in the same subsection have the same filter they
are merged on the next save, taking the union of the notify types.

For watch configurations that notify on no event the list of notify
types is empty:

  [project "foo"]
    notify = branch:master []

Unknown notify types are ignored and removed on save.

To support a live migration on a multi-master Gerrit installation, the
upgrade is done in 2 steps:

- part 1 (this change):
  * always write to both backends (database and git)
  * a configuration option (user.readProjectWatchesFromGit) decides if
    the project watches are read from database or git (default:
    database)
  * upgraded instances write to both backends, old instances only
    read/write from/to the database
  * after upgrading all instances (all still read from the database)
    run a batch to copy all project watches from the database to git
  * update all instances to read from git
  * make sure all instances use the new schema version of the account
    index
- part 2 (next change):
  * bump the database schema version
  * migrate the project watches from database to git (for single
    instance Gerrit servers)
  * delete the database table
  * delete the user.readProjectWatchesFromGit config option

This change requires that the account cache is manually evicted.

Change-Id: I4f8d4e8a762aeb4b46e27bb3bf9e58f91611145d
Signed-off-by: Edwin Kempin <ekempin@google.com>

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/client/ProjectWatchInfo.java

@@ -47,4 +47,30 @@ public class ProjectWatchInfo {
         .hash(project, filter, notifyNewChanges, notifyNewPatchSets,
             notifyAllComments, notifySubmittedChanges, notifyAbandonedChanges);
   }
+
+  @Override
+  public String toString() {
+    StringBuilder b = new StringBuilder();
+    b.append(project);
+    if (filter != null) {
+      b.append("%filter=")
+          .append(filter);
+    }
+    b.append("(notifyAbandonedChanges=")
+        .append(toBoolean(notifyAbandonedChanges))
+        .append(", notifyAllComments=")
+        .append(toBoolean(notifyAllComments))
+        .append(", notifyNewChanges=")
+        .append(toBoolean(notifyNewChanges))
+        .append(", notifyNewPatchSets=")
+        .append(toBoolean(notifyNewPatchSets))
+        .append(", notifySubmittedChanges=")
+        .append(toBoolean(notifySubmittedChanges))
+        .append(")");
+    return b.toString();
+  }
+
+  private boolean toBoolean(Boolean b) {
+    return b == null ? false : b;
+  }
 }