bundle progress: offer best-guess deterministic progress information This uses the same strategy as progress for pulls, estimating manifests based on changeset count and estimating file count by files list in each changeset.

httpsendfile: record progress information during read() This allows us to provide deterministic progress information during transfer of bundle data over HTTP. This is required because we currently buffer the bundle data to local disk prior to transfer since wsgiref lacks chunked transfer-coding support.