lfs: explicitly add the Content-Length header when uploading blobs, for py3 This was the reason for test-lfs-test-server.t#git-server complaining about an "invalid byte in chunk length". For some reason if this isn't explicitly added, py3.7.1 is adding `transfer-encoding: chunked` as well as `Content-length: x`. Wireshark flagged this as malformed. However, if this is set, it doesn't bother with `transfer-encoding`. Before this patch with py3: PUT /objects/31cf46fbc4ecd458a0943c5b4881f1f5a6dd36c53d6167d5b69ac45149b38e5b HTTP/1.1 Accept-Encoding: identity Content-length: 12 accept: application/vnd.git-lfs content-type: application/octet-stream host: localhost:20062 transfer-encoding: chunked user-agent: git-lfs/2.3.4 (Mercurial 4.9rc0+149-7eb7637e34bf) Before this patch with py27: PUT /objects/31cf46fbc4ecd458a0943c5b4881f1f5a6dd36c53d6167d5b69ac45149b38e5b HTTP/1.1 Accept-Encoding: identity accept: application/vnd.git-lfs content-type: application/octet-stream content-length: 12 host: localhost:20062 user-agent: git-lfs/2.3.4 (Mercurial 4.9rc0+149-7eb7637e34bf+20190128) With this patch and py3, the content is the same as the py27 example. RFC2616 says to ignore `Content-Length` if `Transfer-Encoding` is present, so maybe there's nothing to do in the hg-server side (though I'm not sure which it is using if presented both). Maybe chunked encoding is better to do? If someone knows how to suppress the `Content-Length`, we can try that instead.

perf: support looking up multiple revisions The nodemap code has optimisations around the number of lookup we actually made. As a result, being able to specify multiple revisions to look up is important when measuring performances. One can now specify full revspecs with the --rev arguments.

perf: add a no-lookup variant to perfindex It is useful to check how long it takes to create a index object without doing anything with it. We add a new flag dedicated to that.

perf: add some documentation to perfindex It seems useful to document how the arguments can affect the benchmark.

perf: move cache clearing in the `setup` step of `perfheads` The cache clearing is pretty fast, but this seems more "correct".

revlog: document cext oddities in terms of object/caches This clarify why we just call clearcaches on a single object.

perf: document perfheads

py3: stabilize the output of lfs commandserver tests The print() statements were being output at the very end, so write to the same stdout sink as runcommand, and explicitly flush.

py3: conditionalize some LFS test output I'm not sure why the one stackframe is py2 only, but that seems harmless. The remaining failure is LfsCorruptionError printing the fully qualified name, as well as b'' around its message.

lfs: strip the response headers from the Batch API before printing For reasons unknown, py3 is adding an extra '\n' before the headers print out. This makes the output the same as py2.