Allow to use /a/ prefix on push to apache-git-http-backend

The replication plugin will try to fetch, if replication of all refs
is requested. This fetch will usually need to be authenticated, since
it is routed to Gerrit. Thus, the URL used for replication needs the
/a/ prefix. However, the apache-git-http-backend couldn't use it
for the git-backend, since it would assume that /a/ is part of the
repo path.

Now /a/ was added as a ScriptAlias, allowing to use it as a prefix.

Change-Id: I625aa610416978c4b1d4625ce5dc5a89f6d8a84d

container-images/apache-git-http-backend/config/git-http-backend.conf

diff --git a/container-images/apache-git-http-backend/config/git-http-backend.conf b/container-images/apache-git-http-backend/config/git-http-backend.conf
index e6bf8d5..9fb7b88 100644
--- a/container-images/apache-git-http-backend/config/git-http-backend.conf
+++ b/container-images/apache-git-http-backend/config/git-http-backend.conf
@@ -16,6 +16,8 @@
   SetEnv GIT_PROJECT_ROOT /var/gerrit/git
   SetEnv GIT_HTTP_EXPORT_ALL
   ScriptAliasMatch "(?i)^/a/projects/(.*)" "/var/cgi/project_admin.sh"
+
+  ScriptAlias /a/ /usr/libexec/git-core/git-http-backend/
   ScriptAlias / /usr/libexec/git-core/git-http-backend/
   ScriptLog logs/cgi.log