Fix version upgrade check for prerelease versions (#4407)

# Description of Changes

Fix our version compatibility checking for prereleases. Fixes
https://github.com/clockworklabs/SpacetimeDB/issues/4405.

# API and ABI breaking changes

None.

# Expected complexity level and risk

1

# Testing
I've added more unit tests for the upgrade behavior surrounding
prereleases (upgrading to a prerelease, upgrading from a prerelease, and
upgrading between prereleases).

---------

Co-authored-by: Zeke Foppa <bfops@users.noreply.github.com>

crates/core/src/config.rs

@@ -63,6 +63,12 @@ impl MetadataFile {
             previous.edition,
         );
 
+        // This is mostly redundant with the caret comparison below, but
+        // pre-releases make it annoying.
+        if previous.version == current.version {
+            return Ok(());
+        }
+
         // Special-case: SpacetimeDB 2.x can run 1.x databases.
         if previous.version.major == 1 && current.version.major == 2 {
             return Ok(());
@@ -73,7 +79,8 @@ impl MetadataFile {
             major: previous.version.major,
             minor: Some(previous.version.minor),
             patch: None,
-            pre: previous.version.pre.clone(),
+            // We deal with pre-releases separately above.
+            pre: semver::Prerelease::new("").unwrap(),
         };
 
         if cmp.matches(&current.version) {
@@ -170,6 +177,16 @@ mod tests {
         semver::Version::new(major, minor, patch)
     }
 
+    fn mkver_pre(major: u64, minor: u64, patch: u64, pre: &str) -> semver::Version {
+        semver::Version {
+            major,
+            minor,
+            patch,
+            pre: semver::Prerelease::new(pre).unwrap(),
+            build: semver::BuildMetadata::EMPTY,
+        }
+    }
+
     fn mkmeta(major: u64, minor: u64, patch: u64) -> MetadataFile {
         MetadataFile {
             version: mkver(major, minor, patch),
@@ -178,6 +195,14 @@ mod tests {
         }
     }
 
+    fn mkmeta_pre(major: u64, minor: u64, patch: u64, pre: &str) -> MetadataFile {
+        MetadataFile {
+            version: mkver_pre(major, minor, patch, pre),
+            edition: "standalone".to_owned(),
+            client_connection_id: None,
+        }
+    }
+
     #[test]
     fn check_metadata_compatibility_checking() {
         assert_eq!(
@@ -212,4 +237,37 @@ mod tests {
             .check_compatibility_and_update(mkmeta(3, 0, 0))
             .unwrap_err();
     }
+
+    #[test]
+    fn check_metadata_compatibility_prerelease() {
+        mkmeta(1, 9, 0)
+            .check_compatibility_and_update(mkmeta_pre(2, 0, 0, "rc1"))
+            .unwrap();
+
+        mkmeta_pre(2, 0, 0, "rc1")
+            .check_compatibility_and_update(mkmeta_pre(2, 0, 0, "rc1"))
+            .unwrap();
+
+        mkmeta_pre(2, 0, 0, "rc1")
+            .check_compatibility_and_update(mkmeta(2, 0, 1))
+            .unwrap();
+
+        mkmeta_pre(2, 0, 0, "rc1")
+            .check_compatibility_and_update(mkmeta(2, 0, 0))
+            .unwrap();
+
+        // Now check some failures..
+
+        mkmeta_pre(2, 0, 0, "rc1")
+            .check_compatibility_and_update(mkmeta_pre(2, 0, 0, "rc2"))
+            .unwrap_err();
+
+        mkmeta_pre(2, 0, 0, "rc2")
+            .check_compatibility_and_update(mkmeta_pre(2, 0, 0, "rc1"))
+            .unwrap_err();
+
+        mkmeta(2, 0, 0)
+            .check_compatibility_and_update(mkmeta_pre(2, 1, 0, "rc1"))
+            .unwrap_err();
+    }
 }