Use a new Mason environment variable instead of a set location

Adds `MASON_LICENSE_CACHE_PATH` as something that Mason understands, and when it
is specified, use it with `--reference-if-able` when downloading the license
repository.

Updates the test EXECENV to set this environment variable to REPO_CACHE_PATH,
which we use for other cached repositories in nightly testing, but only if that
environment variable is defined.  This should allow fellow team members to not
have to set this environment variable (because they probably won't need it)

----
Signed-off-by: Lydia Duncan <lydia-duncan@users.noreply.github.com>

test/mason/EXECENV

@@ -1,9 +1,19 @@
+#!/usr/bin/env python3
+
+import os
+
 # Ensure mason in PATH
-PATH=$CHPL_HOME/bin/$CHPL_HOST_BIN_SUBDIR:$PATH
+print('PATH=$CHPL_HOME/bin/$CHPL_HOST_BIN_SUBDIR:$PATH')
 
 # Mason envs
-MASON_HOME=$PWD/mason_home
+print('MASON_HOME=$PWD/mason_home')
+
 # Note, this registry should only ever be used by mason update tests
-MASON_REGISTRY=registry|https://github.com/chapel-lang/mason-registry
-MASON_OFFLINE=false
-SPACK_ROOT=$PWD/mason_home/spack
+
+print('MASON_REGISTRY=registry|https://github.com/chapel-lang/mason-registry')
+print('MASON_OFFLINE=false')
+print('SPACK_ROOT=$MASON_HOME/spack')
+
+cachePath = os.getenv('REPO_CACHE_PATH', default='')
+if cachePath != '':
+   print('MASON_LICENSE_CACHE_PATH=' + cachePath)

tools/mason/MasonEnv.chpl

@@ -112,6 +112,16 @@ proc MASON_REGISTRY {
   return registries;
 }
 
+/* Returns the path to use when caching the list of licenses, if provided by the
+   user.  This is useful for systems where internet connectivity can be erratic
+   or slow.
+ */
+proc MASON_LICENSE_CACHE_PATH: string {
+  const licenseCache = getEnv("MASON_LICENSE_CACHE_PATH");
+
+  return licenseCache;
+}
+
 proc masonEnv(args) {
 
   var parser = new argumentParser(helpHandler=new MasonEnvHelpHandler());

tools/mason/MasonPublish.chpl

@@ -690,7 +690,8 @@ proc refreshLicenseList(overwrite=false) throws {
   const branch = '--branch main ';
   const depth = '--depth 1 ';
   const url = 'https://github.com/spdx/license-list-data.git ';
-  const referIfAble = " --reference-if-able " + dest;
+  const referIfAble = if MASON_LICENSE_CACHE_PATH != "" then
+    " --reference-if-able " + MASON_LICENSE_CACHE_PATH + "/spdx" else "";
   const command = 'git clone -q ' + branch + depth + url + dest + referIfAble;
   if !isDir(dest) {
     runCommand(command);