Summary:
Introduced a new local commit metadata storage system, smallcommitmetadata, which stores a simple local JSON file for a mapping of (node, category) -> value.
This data can be manipulated with the debugsmallcommitmetadata command, and can be consumed in the smartlog using the smallcommitmeta template func.
Total number of entries can be limited with smallcommitmetadata.entrylimit configuration option, which defaults to 100.
Reviewed By: DurhamG
Differential Revision: D21673611
fbshipit-source-id: 2239a47867118dd86b15944058505ddf67548549
