add site.less, for defining site-specific Less rules

Admins can (either by hand, or in a separate RPM) overwrite the
site.less symlink to point at their own custom Less rules, which will be
included with Beaker's Less sources when generating CSS.

Ideally this would just be a config option of extra filenames which are
appended to the 'css' assets bundle. Unfortunately that doesn't work
because webassets compiles each Less source file separately, which
prevents the site Less rules from overriding or cross-referencing the
Beaker ones.

In future Less might support @import globs [1] which would allow us to
@import site rules from a defined directory. But until then we have to
do this ghost symlink hackery.

[1] less/less.js#1181

Bug: 1012224
Change-Id: I86f6d6987fd66988a46ec7372bbc3a249f015b46

Server/assets/site.less

@@ -0,0 +1 @@
+/dev/null

Server/assets/style.less

@@ -135,3 +135,8 @@ input.tt-hint {
 @import "reserve-workflow.less";
 @import "job-matrix.less";
 @import "system.less";
+
+// Site-specific styles. The beaker-server package creates site.less as 
+// a symlink to /dev/null if it doesn't exist. Admins can overwrite the symlink 
+// to point at their own custom LESS instead.
+@import "site.less";

Server/bkr/server/assets.py

@@ -108,6 +108,8 @@ def list_asset_sources(source_dir):
     for bundle in env:
         for path in get_all_bundle_files(bundle, env):
             paths.append(os.path.relpath(path, source_dir))
+    # site.less should be skipped because it's a symlink
+    paths.remove('site.less')
     # font-awesome is currently not managed by webassets because webassets 
     # breaks on non-UTF8 input files
     paths.extend([

beaker.spec

@@ -352,6 +352,10 @@ chown root:root %{_localstatedir}/log/%{name}/*.log >/dev/null 2>&1 || :
 chmod go-w %{_localstatedir}/log/%{name}/*.log >/dev/null 2>&1 || :
 # Restart rsyslog so that it notices the config which we ship
 /sbin/service rsyslog condrestart >/dev/null 2>&1 || :
+# Create symlink for site.less (this is ghosted so that other packages can overwrite it)
+if [ ! -f %{_datadir}/bkr/server/assets/site.less ] ; then
+    ln -s /dev/null %{_datadir}/bkr/server/assets/site.less || :
+fi
 %endif
 
 %if %{with labcontroller}
@@ -469,6 +473,7 @@ rm -rf %{_var}/lib/beaker/osversion_data
 %attr(-,apache,root) %dir %{_datadir}/bkr
 %attr(-,apache,root) %{_datadir}/bkr/beaker-server.wsgi
 %attr(-,apache,root) %{_datadir}/bkr/server
+%ghost %attr(0777,root,root) %{_datadir}/bkr/server/assets/site.less
 %attr(0660,apache,root) %config(noreplace) %{_sysconfdir}/%{name}/server.cfg
 %dir %{_localstatedir}/log/%{name}
 %dir %{_localstatedir}/cache/%{name}