Bug 527670: Add documentation to update-verify clear_cache() r=aki

Added documentation to methods, missed from last PR

Differential Revision: https://phabricator.services.mozilla.com/D129667

tools/update-verify/release/common/cached_download.sh

@@ -8,6 +8,9 @@ popd &>/dev/null
 
 # Deletes all files in the cache directory
 # We don't support folders or .dot(hidden) files
+# By not deleting the cache directory, it allows us to use Docker tmpfs mounts,
+# which are the only workaround to poor mount r/w performance on MacOS
+# Reference: https://forums.docker.com/t/file-access-in-mounted-volumes-extremely-slow-cpu-bound/8076/288
 clear_cache () {
     rm -rf "${cache_dir}/*"
 }

tools/update-verify/release/updates/verify.sh

@@ -7,7 +7,7 @@
 . ../common/download_builds.sh
 . ../common/check_updates.sh
 
-# Cache being handled by new async_download.py
+# Cache init being handled by new async_download.py
 # clear_cache
 # create_cache
 
@@ -103,10 +103,10 @@ fi
 while read entry
 do
   # initialize all config variables
-  release="" 
-  product="" 
-  platform="" 
-  build_id="" 
+  release=""
+  product=""
+  platform=""
+  build_id=""
   locales=""
   channel=""
   from=""