pager: recreate stdout to make it line-buffered We want to see partial command results as soon as possible. But the buffering mode of stdout (= pager's stdin) was set to fully-buffered because it isn't associated with a tty. So, this patch recreates new stdout object to force its buffering mode. Because two file objects are associated with the same stdout fd and their destructors will call close(), one of them must be closed carefully. Python expects that the stdout fd never be closed even after sys.stdout.close() [1], but newstdout has no such hack. So this patch calls newstdout.close() immediately before duplicating the original stdout fd to sys.stdout. operation sys.stdout newstdout fd --------------------- ---------- --------- -------- newstdout.close() open closed closed os.dup2(stdoutfd, ..) open closed open del sys.stdout closed closed open [1] [1]: https://hg.python.org/cpython/file/v2.7.10/Python/sysmodule.c#l1391

pager: rename variables of backup fds The next patch will add backup file objects, so the original variable names would be confusing.

pager: inline _pagersubprocess() into _runpager() We don't need _pagersubprocess() because the fork version was removed at 59d794154e8d.

ui: send traceback of devel warning to appropriate output stream If ui.ferr is a command-server channel, traceback should be written to it.

util.system: compare fileno to see if it needs stdout redirection Future patches will reopen stdout to be line-buffered, so sys.stdout may be different object than sys.__stdout__.

exchange: move stream clone logic into pull code path Stream clones are a special case of clones. Clones are a special case of pull. Most of the logic for deciding what to do at pull time is in exchange.py. It makes sense for the stream clone determination to live there as well. This patch moves the calling of the stream clone code into pull(). The checks in streamclone.canperformstreamclone() ensure that we don't perform a stream clone unless it is possible. A future patch will convert maybeperformstreamclone() to accept a pullop to make it consistent with everything else in pull(). It will also grow some functionality (in case you doubted the necessity of a 4 line function).

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.