sshpeer: return framed file object when needed Currently, wireproto.wirepeer has a default implementation of _submitbatch() and sshv1peer has a very similar implementation. The main difference is that sshv1peer is aware of the total amount of bytes it can read whereas the default implementation reads the stream until no more data is returned. The default implementation works for HTTP, since there is a known end to HTTP responses (either Content-Length or 0 sized chunk). This commit teaches sshv1peer to use our just-introduced "cappedreader" class for wrapping a file object to limit the number of bytes that can be read. We do this by introducing an argument to specify whether the response is framed. If set, we returned a cappedreader instance instead of the raw pipe. _call() always has framed responses. So we set this argument unconditionally and then .read() the entirety of the result. Strictly speaking, we don't need to use cappedreader in this case and can inline frame decoding/read logic. But I like when things are consistent. The overhead should be negligible. _callstream() and _callcompressable() are special: whether framing is used depends on the specific command. So, we define a set of commands that have framed response. It currently only contains "batch." As a result of this change, the one-off implementation of _submitbatch() in sshv1peer can be removed since it is now safe to .read() the response's file object until end of stream. cappedreader takes care of not overrunning the frame. Differential Revision: https://phab.mercurial-scm.org/D2380

sshpeer: move logic for sending a request into a new function The **args being used to pass arbitrary command arguments is limiting because it makes it harder to control behavior of the function. We factor most of _callstream() into a new function that doesn't use **args. Differential Revision: https://phab.mercurial-scm.org/D2379

help: fix wording describing SSH requirements

graphlog: document what "_" and "*" mean Documenting "*" should've been a part of 9b3f95d9783d, but I somehow didn't notice that the symbols are explained in the command's help text.

sshpeer: rename _recv and _send to _readframed and _writeframed Because it is reading and writing a chunk of data with a well-defined size. "recv" and "send" make it sound like things are a direct proxy to the underlying pipe, which they aren't. Differential Revision: https://phab.mercurial-scm.org/D2378

util: add a file object proxy that can read at most N bytes Sometimes we have data of a known size within a stream. For performance reasons, we don't want to pre-read this data (we want to allow consumers to read on demand). For simplicitly reasons, we don't want callers to necessarily know their data is coming from within an outer stream and there is a limit to how much they should read. The class introduced by this commit provides a very simple proxy around an underlying file object that allows the consumer to .read() up to N bytes from the file object. Attempts to read past this many bytes results in a simulated EOF. Differential Revision: https://phab.mercurial-scm.org/D2377

patches: release the GIL while applying the patch This will allow multiple threads to apply patches at the same time.

perfbranchmap: allow to select the filter to benchmark Running the branchmap computation on all filter levels can be expensive. Narrowing the run to some specific filters can speed up benchmarking time when working only on a subset of filter levels.

perfbranchmap: display 'unfiltered' for unfiltered performance This is slightly clearer than "None" and will help with coming changes to select the filter level we want timing for.

py3: two more narrow tests passing Differential Revision: https://phab.mercurial-scm.org/D2390