Add migration scripts for historical versions of the definitions format

See README for more information on how the migrations are intended work.

These migrations are probably not widely useful, as our definitions have
already been migrated manually. However, I want to come up with a good
pattern for writing migration scripts, and actually doing it seems like
the best way.

There is a 'migrations/indent' tool, which reformats a set of
definitions according to how the ruamel.yaml program writes them out.
This tool is nice if you like everything to have consistent indent and
line wrapping, and you can run it before running the migrations to
ensure that the migrations don't do any reformatting when writing the
.moprh files back to disk.

The migration scripts require the ruamel.yaml Python library. I have
sent a separate change to add this to the 'build' and 'devel' reference
systems.

Change-Id: Ibd62ba140d3f7e8e638beed6d714f671405bdc79

1 files changed, 78 insertions, 0 deletions

diff --git a/migrations/005-strip-commands.py b/migrations/005-strip-commands.py
new file mode 100755
index 00000000..da3de940
--- /dev/null
+++ b/migrations/005-strip-commands.py
@@ -0,0 +1,78 @@
+#!/usr/bin/env python
+# Copyright (C) 2015  Codethink Limited
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+'''Migration to Baserock Definitions format version 5.
+
+Version 5 of the definitions format adds a 'strip-commands' field that can
+be set in chunk definitions.
+
+Version 5 also allows deployment extensions to live in definitions.git instead
+of morph.git. This greatly reduces the interface surface of the Baserock
+definitions format specification, because we no longer have to mark a new
+version of the definitions format each time an extension in morph.git is added,
+removed, or changes its API in any way.
+
+In commit 6f4929946 of git://git.baserock.org/baserock/baserock/definitions.git
+the deployment extensions were moved into an extensions/ subdirectory, and the
+system and cluster .morph files that referred to them were all updated to
+prepend 'extension/' to the filenames. This migration doesn't (re)do that
+change.
+
+'''
+
+
+import sys
+import warnings
+
+import migrations
+
+
+TO_VERSION = 5
+
+
+def check_strip_commands(contents, filename):
+    assert contents['kind'] == 'chunk'
+
+    valid = True
+
+    if 'strip-commands' in contents:
+        warnings.warn(
+            "%s has strip-commands, which are not valid until version 5" %
+            filename)
+        valid = False
+
+    return valid
+
+
+try:
+    if migrations.check_definitions_version(TO_VERSION - 1):
+        safe_to_migrate = migrations.process_definitions(
+            kinds=['chunk'], validate_cb=check_strip_commands)
+
+        if not safe_to_migrate:
+            sys.stderr.write(
+                "Migration failed due to one or more warnings.\n")
+            sys.exit(1)
+        else:
+            migrations.set_definitions_version(TO_VERSION)
+            sys.stdout.write("Migration completed successfully.\n")
+            sys.exit(0)
+    else:
+        sys.stdout.write("Nothing to do.\n")
+        sys.exit(0)
+except RuntimeError as e:
+    sys.stderr.write("Error: %s\n" % e.message)
+    sys.exit(1)