add 'db migrate' command option to specify target version

src/cli.rs

@@ -3,7 +3,7 @@
 //! CLI argument structs are defined in this module. Execution logic for each
 //! command goes in a submodule.
 
-use std::path::PathBuf;
+use std::{path::PathBuf, str::FromStr};
 
 use clap::{Parser, Subcommand};
 
@@ -78,6 +78,23 @@ pub(crate) struct MigrateDbArgs {
     #[clap(flatten)]
     config: ConfigArg,
 
+    /// Target server implementation to migrate database to.
+    ///
+    /// If migrating to the current version of grapevine, specify the version
+    /// as 'grapevine'.
+    ///
+    /// If migrating to a released version of conduit, specified the version
+    /// of conduit as `conduit-{version}` (example: `conduit-0.8.0`). If
+    /// migrating to an unreleased conduit build, instead specify the raw
+    /// database version as `conduit-db-{version}` (example: `conduit-db-13`).
+    /// The raw database version can be found by looking at the
+    /// `latest_database_version` variable in `src/database/mod.rs`.
+    ///
+    /// The server implementation used for the current database will be
+    /// detected automatically, and does not need to be specified.
+    #[clap(long)]
+    pub(crate) to: DbMigrationTarget,
+
     /// Path to read database from.
     #[clap(long = "in", short)]
     pub(crate) in_path: PathBuf,
@@ -87,6 +104,78 @@ pub(crate) struct MigrateDbArgs {
     pub(crate) out_path: PathBuf,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) enum DbMigrationTarget {
+    /// The latest grapevine db version
+    ///
+    /// Example:
+    ///
+    /// ```
+    /// assert_eq!("grapevine".parse(), Ok(DbMigrationTarget::Grapevine))
+    /// ```
+    Grapevine,
+    /// A conduit-compatible db version.
+    ///
+    /// This may either be specified as a released version number or directly
+    /// as a database version. The raw database version must be used when
+    /// migrating to a conduit deployment built from an unreleased commit
+    /// on the `next` branch.
+    Conduit(ConduitDbVersion),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) enum ConduitDbVersion {
+    /// A conduit release version number
+    ///
+    /// Example:
+    ///
+    /// ```
+    /// assert_eq!(
+    ///     "conduit-0.8.0".parse(),
+    ///     Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Release("0.8.0")))
+    /// );
+    /// ```
+    Release(String),
+    /// A raw database version
+    ///
+    /// This corresponds directly to a
+    /// [`crate::service::globals::DbVersion::Conduit`] version.
+    ///
+    /// Example:
+    ///
+    /// ```
+    /// assert_eq!(
+    ///     "conduit-db-13".parse(),
+    ///     Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Db(13)))
+    /// );
+    /// ```
+    Db(u64),
+}
+
+#[derive(thiserror::Error, Debug)]
+#[error("invalid db migration target version")]
+pub(crate) struct DbMigrationTargetParseError;
+
+impl FromStr for DbMigrationTarget {
+    type Err = DbMigrationTargetParseError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if s == "grapevine" {
+            Ok(DbMigrationTarget::Grapevine)
+        } else if let Some(version) = s.strip_prefix("conduit-db-") {
+            let version =
+                version.parse().map_err(|_| DbMigrationTargetParseError)?;
+            Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Db(version)))
+        } else if let Some(version) = s.strip_prefix("conduit-") {
+            Ok(DbMigrationTarget::Conduit(ConduitDbVersion::Release(
+                version.to_owned(),
+            )))
+        } else {
+            Err(DbMigrationTargetParseError)
+        }
+    }
+}
+
 impl Args {
     pub(crate) async fn run(self) -> Result<(), error::Main> {
         match self.command {