histedit: explain basics of histedit commands This should be hooked into @action via an extended help argument, but that is future work.

histedit: report the unacceptable changeset

mdiff: don't emit a diff header for empty trivial deltas An empty trivial delta, coded as (0, 0, 0) makes the delta application do nothing, but still takes 12 bytes, while skipping it altogether works as much, without taking any space at all.

commands: get rid of empty try/finally block from _dograft This diff is purely an indentation change to clean up a block that was kept in place to make 77995317b374 easier to read.

commands: get rid of empty try/finally block from _dobackout This diff is purely an indentation change to clean up a block that was kept in place to make c7217f1458bf easier to read.

commands: get rid of empty try/finally block from import_ This diff is purely an indentation change to clean up a block that was kept in place to make 713b09fc9fbb easier to read.

streamclone: use context manager for writing files These are the file writes that have the most to gain from background I/O. Plug in a context manager so I can design the background I/O mechanism with context managers in mind.

scmutil: use context managers for file handles Now that we dropped support for Python 2.4, we are able to use context managers. Let's replace the try..finally pattern in scmutil.py with context managers, which close files automatically when the context manager is exited. There should be no change in behavior with this patch. Why convert to context managers if nothing is broken? I'm working on closing file handles in background threads to improve performance on Windows. As part of this, I realized there could be some future issues if the background file closing code isn't designed with context managers in mind. So, I'd like to switch some code to context managers so I can design an API that works with context managers.

statichttprepo: implement __enter__ and __exit__ on httprangeheader httprangeheader behaves like a file object. Implement __enter__ and __exit__ so it can be used as a context manager, just like file objects.

osutil: implement __enter__ and __exit__ on posixfile So they can be used as context managers.