treat all refs/users/.* references as internal and to be ignored

We noticed that Gerrit can create some references using the following
naming scheme:

    refs/users/<last-2-digits-of-userid>/<userid>

When it does, this causes the hooks to fail with a message indicating
that it is unable to determine the type of reference it is, because
it doesn't recognize it.

This commit changes the hooks.ignore-refs default configuration
to ignore all references whose name start with "refs/users/".
We could be stricter in our matching, but I think this would be
slightly overkill. And meanwhile, we can see that this is not
the first time we notice that references in the "refs/users/"
namespace where created by Gerrit (e.g. we were already ignoring
references matching "refs/users/.*/edit-.*" before). So, being
being more relaxed here helps us avoid having to change the config
again in the future should Gerrit decide to expand on its use of
this namespace.

Change-Id: I3196cfc833ac94473d4b5fcdca773ded4ced24cf
TN: V218-013

Author: brobecke

hooks/config.py

@@ -18,7 +18,7 @@
 # being garbage-collected.
 GERRIT_INTERNAL_REFS = (
     "refs/changes/.*",
-    "refs/users/.*/edit-.*",
+    "refs/users/.*",
     "refs/cache-automerge/.*",
     "refs/sequences/.*",
     "refs/groups/.*",

testsuite/tests/V218-013__ignore_refs_users_gerrit_ref/bare_repo_config

@@ -0,0 +1,4 @@
+[core]
+	repositoryformatversion = 0
+	filemode = true
+	bare = true

testsuite/tests/V218-013__ignore_refs_users_gerrit_ref/git-repos.tar.bz2

@@ -0,0 +1,4 @@
+[hooks]
+        from-domain = adacore.com
+        mailinglist = git-hooks-ci@example.com
+        filer-email = filer@example.com

testsuite/tests/V218-013__ignore_refs_users_gerrit_ref/hooks_config

@@ -0,0 +1,21 @@
+def test_push_commit_to_ignored_ref(testcase):
+    """Try pushing master to a reference that's configured to be ignored."""
+
+    # Simulate one action that Gerrit does, which is to create
+    # some "Special references" which are internal to its operations.
+    # For instance, "refs/users/<last-2-digits-of-userid>/<userid>".
+    #
+    # The purpose of this testcase is to verify that the push is completely
+    # ignored by the git-hooks (in particular no check, no style check, and
+    # no emails).
+
+    p = testcase.run("git push origin master:refs/users/01/104201".split())
+    expected_out = testcase.massage_git_output(
+        """\
+To ../bare/repo.git
+ * [new reference]   master -> refs/users/01/104201
+"""
+    )
+
+    testcase.assertEqual(p.status, 0, p.image)
+    testcase.assertRunOutputEqual(p, expected_out)