Change default push refSpec to 'refs/*:refs/*' (non-forced push)

Using forced push as implicit default for replication to slaves
could lead to unintended disruption on remote repositories.
Default git push refSpec is non-forced so the user would expect
Gerrit replication to apply the same default behaviour.

See: http://bit.ly/1jEU2vp for disruption caused by default forced push
Change-Id: I4509d3500c730b8b5921dc155ea0476a70b3de9e

src/main/java/com/googlesource/gerrit/plugins/replication/ReplicationFileBasedConfig.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/ReplicationFileBasedConfig.java b/src/main/java/com/googlesource/gerrit/plugins/replication/ReplicationFileBasedConfig.java
index 60a3918..0e3894b 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/ReplicationFileBasedConfig.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/ReplicationFileBasedConfig.java
@@ -118,8 +118,7 @@
       }
 
       if (c.getPushRefSpecs().isEmpty()) {
-        c.addPushRefSpec(new RefSpec().setSourceDestination("refs/*", "refs/*")
-            .setForceUpdate(true));
+        c.addPushRefSpec(new RefSpec().setSourceDestination("refs/*", "refs/*"));
       }
 
       Destination destination =

src/main/resources/Documentation/config.md

diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index 04f907c..9521375 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -128,13 +128,20 @@
 	the active branches, but not the change refs under
 	`refs/changes/`, or the tags under `refs/tags/`.
 
+	Note that prefixing a source refspec with `+` causes the replication
+	to be done with a `git push --force` command.
+	Be aware that when you are pushing to remote repositories that may
+	have read/write access (e.g. GitHub) you may want to omit the `+`
+	to prevent the risk of overwriting branches that have been modified
+	on the remote.
+
 	Multiple push keys can be supplied, to specify multiple
 	patterns to match against.  In the [example above][2], remote
 	"pubmirror" uses two push keys to match both `refs/heads/*`
 	and `refs/tags/*`, but excludes all others, including
 	`refs/changes/*`.
 
-	Defaults to `+refs/*:refs/*` (all refs) if not specified.
+	Defaults to `refs/*:refs/*` (push all refs) if not specified.
 
 [2]: #example_file