Clarify messages

This is mainly to avoid the effect of specifically recommending
that the release version/name (usually taken from a tag) be
changed to match the version in Cargo.toml, which would not always
be good advice because it may be that the version in Cargo.toml
is wrong, or that both are wrong, or in testing that a specially
named tag (or `VERSION` environment variable) should be used.

.github/workflows/release.yml

@@ -45,17 +45,19 @@ jobs:
 
           case "$VERSION" in
           "v$manifest_version" )
-            echo 'OK: Version to name the relase agrees with top-level Cargo.toml.'
+            echo 'OK: Release name/version agrees with Cargo.toml version.'
             ;;
           TEST-* | *-DO-NOT-USE )
-            echo 'OK: Version to name the release is strange but marked as such.'
+            echo 'OK: Release name/version is strange but marked as such.'
             ;;
           "$manifest_version" )
-            echo 'STOPPING: Version to name the release is missing the leading "v".'
+            echo 'STOPPING: Release name/version is missing the leading "v".'
             exit 1
             ;;
           * )
-            echo 'STOPPING: Version to name the release seems mistaken.'
+            echo 'STOPPING: Release name/version and Cargo.toml version do not match.'
+            echo 'STOPPING: Usually this means either a wrong tag name or wrong version in Cargo.toml.'
+            echo 'STOPPING: If intended, prepend `TEST-` or append `-DO-NOT-USE` to the release name.'
             exit 1
             ;;
           esac