Add documentation of "commit already exists" error message
The "commit already exists" error is similar to "no new changes",
but occurs if the user tries to push to `refs/changes/n` when the
commit already exists on change `n`.
Change-Id: Ifc558d7adc59fb8df5690dfe879b7cc3574ff9f2
diff --git a/Documentation/error-commit-already-exists.txt b/Documentation/error-commit-already-exists.txt
new file mode 100644
index 0000000..dc32c4c1
--- /dev/null
+++ b/Documentation/error-commit-already-exists.txt
@@ -0,0 +1,14 @@
+commit already exists
+=====================
+
+With this error message Gerrit rejects to push a commit to an
+existing change via `refs/changes/n` if the commit was already
+successfully pushed to the change. In this case there is no
+new commit and consequently there is nothing for Gerrit to do.
+
+For further information about how to resolve this error, please
+refer to link:error-no-new-changes.html[no new changes].
+
+GERRIT
+------
+Part of link:error-messages.html[Gerrit Error Messages]
