merge with stable

debugcommands: sort command order The diff is a bit large but it is straight code moving without any logical modifications.

tests: add test that @commands in debugcommands.py are sorted I felt like inline Python in test-check-code.t was the most appropriate place for this, as other linters in contrib/ seem to be source file agnostic. The test currently fails.

fsmonitor: be robust in the face of bad state fsmonitor could write out bad state if interrupted part way through, and would then crash when it tried to read it back in. Make both sides of the operation more robust - reading state should fail cleanly, and we can use atomictemp to write out cleanly as the file is small. Between the two, we shouldn't crash with an IndexError any more.

merge: use original file extension for temporary files Some merge tools (like Araxis?) can pick merge mode based on the file extension. That didn't work well when temporary files were given random suffixes. It seems to work better when the random part is before the extension. As usual, when using $output, $local will have the .orig extension. That could perhaps be the subject of another change another day.

ui: use try..finally in configoverride @contextmanager almost always have their "yield" inside a try..finally block. This is because if the calling code inside the activated context manager raises, the code after the "yield" won't get executed. A "finally" block, however, will get executed in this scenario.

util: limit output chunk size in zlib decompression This is essentially a port of 65bd4b8e48bd, which was inadvertently dropped by 8cd7d0fefd30.