install-files: Allow definition of manifests in multiple variables

install-files was initially designed such that if you wanted to install
multiple manifests you should put multiple whitespace separated paths in
the INSTALL_FILES variable.

This is clunky if you want to extend the set of files to install,
particularly in cluster deployments with multiple systems,
as otherwise you could make use of YAML merge keys.

So now, like fstab.configure you can set multple options, by using
environment variables that start with INSTALL_FILES.

It's also easier to extend the set of install files on the command-line
or in the environment this way too, since you don't need to parse the
YAML to see what it originally had.

Change-Id: I298db7ae9790a536e5a5f32b069d0908012695af

1 files changed, 7 insertions, 5 deletions

diff --git a/extensions/install-files.configure b/extensions/install-files.configure
index 64fcecca..782065d1 100755
--- a/extensions/install-files.configure
+++ b/extensions/install-files.configure
@@ -16,7 +16,7 @@
 
 ''' A Morph configuration extension for adding arbitrary files to a system
 
-It will read the manifest files specified in the environment variable
+It will read the manifest files specified in environment variables starting
 INSTALL_FILES, then use the contens of those files to determine which files
 to install into the target system.
 
@@ -41,12 +41,14 @@ import writeexts
 class InstallFilesConfigureExtension(writeexts.Extension):
 
     def process_args(self, args):
-        if not 'INSTALL_FILES' in os.environ:
+        if not any(var.startswith('INSTALL_FILES') for var in os.environ):
             return
         target_root = args[0]
-        manifests = shlex.split(os.environ['INSTALL_FILES'])
-        for manifest in manifests:
-            self.install_manifest(manifest, target_root)
+        for manifest_var in sorted((var for var in os.environ
+                                    if var.startswith('INSTALL_FILES'))):
+            manifests = shlex.split(os.environ[manifest_var])
+            for manifest in manifests:
+                self.install_manifest(manifest, target_root)
 
     def install_manifest(self, manifest, target_root):
         manifest_dir = os.path.dirname(manifest)