feat! store schema version of generation database in the db

Add a new mandatory database table "meta" to the SQLite database the
stores information about the files in a backup generation. The idea is
for future versions of the Obnam client to be able to be able to
restore from backups made by older -- or newer -- versions of Obnam,
as far as is reasonable.

Add the `obnam gen-info` command to show information about the
generation metadata.

Sponsored-by: author

1 files changed, 36 insertions, 0 deletions

diff --git a/src/cmd/gen_info.rs b/src/cmd/gen_info.rs
new file mode 100644
index 0000000..6d12bd8
--- /dev/null
+++ b/src/cmd/gen_info.rs
@@ -0,0 +1,36 @@
+use crate::client::AsyncBackupClient;
+use crate::config::ClientConfig;
+use crate::error::ObnamError;
+use log::info;
+use structopt::StructOpt;
+use tempfile::NamedTempFile;
+use tokio::runtime::Runtime;
+
+#[derive(Debug, StructOpt)]
+pub struct GenInfo {
+    #[structopt()]
+    gen_ref: String,
+}
+
+impl GenInfo {
+    pub fn run(&self, config: &ClientConfig) -> Result<(), ObnamError> {
+        let rt = Runtime::new()?;
+        rt.block_on(self.run_async(config))
+    }
+
+    async fn run_async(&self, config: &ClientConfig) -> Result<(), ObnamError> {
+        let temp = NamedTempFile::new()?;
+
+        let client = AsyncBackupClient::new(config)?;
+
+        let genlist = client.list_generations().await?;
+        let gen_id = genlist.resolve(&self.gen_ref)?;
+        info!("generation id is {}", gen_id.as_chunk_id());
+
+        let gen = client.fetch_generation(&gen_id, temp.path()).await?;
+        let meta = gen.meta()?;
+        println!("{}", serde_json::to_string_pretty(&meta)?);
+
+        Ok(())
+    }
+}