exchange: teach pull about requested stream clones An upcoming patch will move the invocation of stream cloning logic to the normal pull code path (from localrepository.clone). In preparation for this, we teach pull() and pulloperation about whether a streaming clone is requested. The return logic in localrepository.clone() has been reformatted slightly because of line length issues.

streamclone: add explicit check for empty local repo Stream clone doesn't work with non-empty local repositories. In upcoming patches, we'll move stream cloning to the regular pull code path. Add an explicit check on the repository being empty to prevent streaming clones to non-empty repos.

streamclone: refactor code for deciding to stream clone Having this in a standalone function will eventually enable bundle2 to share code with the bundle1 code path. While I was here, I also added some comments to add clarity.

streamclone: move streaming clone logic from localrepo This is the last remnants of streaming clone code in localrepo.py. This is a mostly mechanical transplant of code to a new file. Only a rewrite of "self" to "repo" was performed. The code will be significantly refactored in upcoming patches. So don't scrutinize it too closely.

streamclone: move _allowstream() from wireproto While we're moving things into streamclone.py...

streamclone: move code out of exchange.py We bulk move functions from exchange.py related to streaming clones. Function names were renamed slightly to drop a component redundant with the module name. Docstrings and comments referencing old names and locations were updated accordingly.

streamclone: move stream_in() from localrepo Another basic content move. The underscore from the function name was removed to comply with naming standards.

streamclone: move applystreamclone() from localrepo.py Upcoming patches will modernize the streaming clone code. Streaming clone data and code kind of lives in its own world. exchange.py is arguably the most appropriate existing location for it. However, over a dozen patches from now it became apparent that there was a lot of code related to streaming clones and that having it contained within its own module would make it easier to comprehend. So, we establish streamclone.py. It's worth noting that streamclone.py existed a long time ago, last seen in the 1.6 release. It was removed in 04f76a954842. The function was renamed as part of the move because its old name was redundant with the new module name. The only other content change was "self" was renamed to "repo" and minor grammar in the docstring was updated.

exchange: add docstring to pull() This seems like the kind of important function that should be documented better.

localrepo: allow creating inherited locks This is part of a series that will allow locks to be inherited by subprocesses in limited circumstances.