Merge with default

Only use expensive fctx.cmp when needed Restrict expensive cmp to cases when: - comparing against working directory and - encode filters active or - path is configured for keyword expansion

Merge with stable

filectx: use ctx.size comparisons to speed up ctx.cmp Comparing sizes is cheaper than comparing file contents, as it does not involve reading the file on disk or from the filelog. It is however not always possible: some extensions, or encode filters, change data when extracting it to the working directory. [ original upstream description ]