Fix latest version resolution when using `python-` prefix (#3056)

Fixes use of version specifiers like `python-3.12`, which:
- have an explicit `python-` prefix
- are using a major version alias that has to be resolved
  to an exact version.

Also simplified the conditional for the already
working case, since it had two branches that were virtually identical.

libexec/pyenv-version-name

@@ -30,11 +30,11 @@ OLDIFS="$IFS"
 { IFS=:
   any_not_installed=0
   for version in ${PYENV_VERSION}; do
-    if version_exists "$version" || [ "$version" = "system" ]; then
-      versions=("${versions[@]}" "${version}")
-    elif version_exists "${version#python-}"; then
-      versions=("${versions[@]}" "${version#python-}")
-    elif resolved_version="$(pyenv-latest -b "$version")"; then
+    # Remove the explicit 'python-' prefix from versions like 'python-3.12'.
+    normalised_version="${version#python-}"
+    if version_exists "${normalised_version}" || [ "$version" = "system" ]; then
+      versions=("${versions[@]}" "${normalised_version}")
+    elif resolved_version="$(pyenv-latest -b "${normalised_version}")"; then
       versions=("${versions[@]}" "${resolved_version}")
     else
       echo "pyenv: version \`$version' is not installed (set by $(pyenv-version-origin))" >&2

test/version-name.bats

@@ -120,3 +120,10 @@ OUT
   assert_success
   assert_output "2.7.11"
 }
+
+@test "pyenv-latest fallback with prefix in name" {
+  create_version "3.12.6"
+  PYENV_VERSION="python-3.12" run pyenv-version-name
+  assert_success
+  assert_output "3.12.6"
+}