Add support for python-version-file

Author: kishaningithub

action.yml

@@ -5,7 +5,7 @@ inputs:
     description: 'Version of python to be installed. Reads from .python-version if unset.'
   python-version-file:
     description: 'Version of python to be installed'
-    default: ".python-version"
+    default: '.python-version'
   cache:
     description: Used to specify whether caching is needed. Set to true, if you'd like to enable caching.
     required: true

find-exact-python-version.sh

@@ -5,10 +5,16 @@ set -euo pipefail
 specified_version="$1"
 specified_version_file="$2"
 
+desired_python_version="${specified_version}"
+
+if [ -f "${specified_version_file}" ]; then
+  desired_python_version=$(cat "${specified_version_file}")
+fi
+
 # This versions map should be kept in sync with
 # - https://www.python.org/downloads/
 # - https://devguide.python.org/versions/
-case "${specified_version}" in
+case "${desired_python_version}" in
     "3")
         echo "3.12.0"
         ;;