Add a new table to store package versions by revision ranges

This isn't new information, but derived from information already in the
database. It's collected here to make querying faster.

The table is updated when each new revision is entered.

sqitch/deploy/package_versions_by_guix_revision_range.sql

@@ -0,0 +1,14 @@
+-- Deploy guix-data-service:package_versions_by_guix_revision_range to pg
+
+BEGIN;
+
+CREATE TABLE package_versions_by_guix_revision_range (
+  git_repository_id integer NOT NULL REFERENCES git_repositories (id),
+  branch_name varchar NOT NULL,
+  package_name varchar NOT NULL,
+  package_version varchar NOT NULL,
+  first_guix_revision_id integer NOT NULL REFERENCES guix_revisions (id),
+  last_guix_revision_id integer NOT NULL REFERENCES guix_revisions (id)
+);
+
+COMMIT;

sqitch/revert/package_versions_by_guix_revision_range.sql

@@ -0,0 +1,7 @@
+-- Revert guix-data-service:package_versions_by_guix_revision_range from pg
+
+BEGIN;
+
+DROP TABLE package_versions_by_guix_revision_range;
+
+COMMIT;

sqitch/sqitch.plan

@@ -20,3 +20,4 @@ change_git_branches_primary_key 2019-08-05T18:57:41Z Christopher Baines <mail@cb
 remove_duplicate_load_new_guix_revision_jobs 2019-08-05T19:06:36Z Christopher Baines <mail@cbaines.net> # Remove duplicate load_new_guix_revision_jobs
 lint_warnings 2019-08-18T17:10:12Z Christopher Baines <mail@cbaines.net> # Store lint warnings
 guix_revision_lint_checkers 2019-09-01T12:17:38Z chris <chris@phact> # Associate lint_checkers to guix_revisions
+package_versions_by_guix_revision_range 2019-09-26T20:23:15Z Christopher Baines <mail@cbaines.net> # Add package_versions_by_guix_revision_range table

sqitch/verify/package_versions_by_guix_revision_range.sql

@@ -0,0 +1,7 @@
+-- Verify guix-data-service:package_versions_by_guix_revision_range on pg
+
+BEGIN;
+
+-- XXX Add verifications here.
+
+ROLLBACK;