containers: introduce 'cirrus-vars' command

The gitlab CI config file has to pass various variables into the cirrus
CI config file to control the build process. This is done by a giant sed
command in the cirrus build template. This is inflexible since the set
of substitutions is hardcoded.

This new 'cirrus-vars' command can replace any variable @NAME@ with the
corresponding value from the $NAME environment variable.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

2 files changed, 21 insertions, 0 deletions

diff --git a/containers/cirrus-run/Dockerfile b/containers/cirrus-run/Dockerfile
index 165f4a8..c59809c 100644
--- a/containers/cirrus-run/Dockerfile
+++ b/containers/cirrus-run/Dockerfile
@@ -1,3 +1,5 @@
 FROM docker.io/library/python:3.9-alpine
 
+COPY cirrus-vars.py /usr/bin/cirrus-vars
+
 RUN pip3 install cirrus-run==1.0.1
diff --git a/containers/cirrus-run/cirrus-vars.py b/containers/cirrus-run/cirrus-vars.py
new file mode 100755
index 0000000..3d863e7
--- /dev/null
+++ b/containers/cirrus-run/cirrus-vars.py
@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+
+import os
+import re
+import sys
+
+var = re.compile(r'@([a-zA-Z0-9_]+)@')
+
+
+# Return empty string if var is not set, since not all
+# OS targets require all vars to be set.
+def get_env(matchobj):
+    return os.environ.get(matchobj.group(1), '')
+
+
+for line in sys.stdin:
+    print(var.sub(get_env, line), end='')
+
+sys.exit(0)