refine 1->3 upgrade process

In hindsight, the "post_tx" step in the upgrade process introduced in
e7f5733 doesn't make sense. If the procedure fails at this stage, nothing says
it still needs to be completed. If the sample file dirs have to be updated
after the database, then there should be another database version to mark that
it's fully completed, and indeed that's the purpose version 3 serves. So get
rid of the Upgrader trait and just go back to a simple run function per
version.

In the case of the sample file dir metadata, it actually can happen before the
database transaction; the stuff written to the database later just needs to be
consistent with what it finds if there's an existing metadata file from a
half-completed update.

For safety, ensure there are no unexpected directory contents before
upgrading 1->2, and ensure the metadata matches before upgrading 2->3.

db/upgrade/v0_to_v1.rs

@@ -36,73 +36,65 @@ use recording;
 use rusqlite;
 use std::collections::HashMap;
 
-pub struct U;
-
-pub fn new<'a>(_args: &'a super::Args) -> Result<Box<super::Upgrader + 'a>, Error> {
-    Ok(Box::new(U))
-}
-
-impl super::Upgrader for U {
-    fn in_tx(&mut self, tx: &rusqlite::Transaction) -> Result<(), Error> {
-        // These create statements match the schema.sql when version 1 was the latest.
-        tx.execute_batch(r#"
-            alter table camera rename to old_camera;
-            create table camera (
-              id integer primary key,
-              uuid blob unique,
-              short_name text not null,
-              description text,
-              host text,
-              username text,
-              password text,
-              main_rtsp_path text,
-              sub_rtsp_path text,
-              retain_bytes integer not null check (retain_bytes >= 0),
-              next_recording_id integer not null check (next_recording_id >= 0)
-            );
-            alter table recording rename to old_recording;
-            drop index recording_cover;
-            create table recording (
-              composite_id integer primary key,
-              camera_id integer not null references camera (id),
-              run_offset integer not null,
-              flags integer not null,
-              sample_file_bytes integer not null check (sample_file_bytes > 0),
-              start_time_90k integer not null check (start_time_90k > 0),
-              duration_90k integer not null
-                  check (duration_90k >= 0 and duration_90k < 5*60*90000),
-              local_time_delta_90k integer not null,
-              video_samples integer not null check (video_samples > 0),
-              video_sync_samples integer not null check (video_samples > 0),
-              video_sample_entry_id integer references video_sample_entry (id),
-              check (composite_id >> 32 = camera_id)
-            );
-            create index recording_cover on recording (
-              camera_id,
-              start_time_90k,
-              duration_90k,
-              video_samples,
-              video_sync_samples,
-              video_sample_entry_id,
-              sample_file_bytes,
-              run_offset,
-              flags
-            );
-            create table recording_playback (
-              composite_id integer primary key references recording (composite_id),
-              sample_file_uuid blob not null check (length(sample_file_uuid) = 16),
-              sample_file_sha1 blob not null check (length(sample_file_sha1) = 20),
-              video_index blob not null check (length(video_index) > 0)
-            );
-        "#)?;
-        let camera_state = fill_recording(tx).unwrap();
-        fill_camera(tx, camera_state).unwrap();
-        tx.execute_batch(r#"
-          drop table old_camera;
-          drop table old_recording;
-        "#)?;
-        Ok(())
-    }
+pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error> {
+    // These create statements match the schema.sql when version 1 was the latest.
+    tx.execute_batch(r#"
+        alter table camera rename to old_camera;
+        create table camera (
+          id integer primary key,
+          uuid blob unique,
+          short_name text not null,
+          description text,
+          host text,
+          username text,
+          password text,
+          main_rtsp_path text,
+          sub_rtsp_path text,
+          retain_bytes integer not null check (retain_bytes >= 0),
+          next_recording_id integer not null check (next_recording_id >= 0)
+        );
+        alter table recording rename to old_recording;
+        drop index recording_cover;
+        create table recording (
+          composite_id integer primary key,
+          camera_id integer not null references camera (id),
+          run_offset integer not null,
+          flags integer not null,
+          sample_file_bytes integer not null check (sample_file_bytes > 0),
+          start_time_90k integer not null check (start_time_90k > 0),
+          duration_90k integer not null
+              check (duration_90k >= 0 and duration_90k < 5*60*90000),
+          local_time_delta_90k integer not null,
+          video_samples integer not null check (video_samples > 0),
+          video_sync_samples integer not null check (video_samples > 0),
+          video_sample_entry_id integer references video_sample_entry (id),
+          check (composite_id >> 32 = camera_id)
+        );
+        create index recording_cover on recording (
+          camera_id,
+          start_time_90k,
+          duration_90k,
+          video_samples,
+          video_sync_samples,
+          video_sample_entry_id,
+          sample_file_bytes,
+          run_offset,
+          flags
+        );
+        create table recording_playback (
+          composite_id integer primary key references recording (composite_id),
+          sample_file_uuid blob not null check (length(sample_file_uuid) = 16),
+          sample_file_sha1 blob not null check (length(sample_file_sha1) = 20),
+          video_index blob not null check (length(video_index) > 0)
+        );
+    "#)?;
+    let camera_state = fill_recording(tx).unwrap();
+    fill_camera(tx, camera_state).unwrap();
+    tx.execute_batch(r#"
+      drop table old_camera;
+      drop table old_recording;
+    "#)?;
+    Ok(())
 }
 
 struct CameraState {