Re: [PATCH v4] gc: save log from daemonized gc --auto and print it next time

Duy Nguyen [off-list ref] writes:

We do keep another lock before coming to opening this log file. So
once we get here we already know nobody else will be opening the log
file. We can simply open it the normal way, then make sure we clean it
up at atexit().

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This doesn't seem like a common thing to want (as in, this might be the
only caller), but it probably makes sense to build it into the
tempfile/lockfile API nevertheless, because implementing it externally
would require a lot of other code to be duplicated.

Another possibility that might work (maybe without requiring changes to
tempfile/lockfile): don't worry about deleting the log file if it is
empty, but make observers treat an empty log file the same as an absent one.

Probably your "don't remove and check for emptiness" approach would
be the simpler of the two, but I think we can go either way.

People have complained to me about stray files in $GIT_DIR, so it's
probably best that we delete empty/useless files. Although we could
delete empty files at the beginning of the next gc instead of at
atexit(). Let me try it out and see which is simplest.

It would be nicer if we did not have to do an extra and custom
atexit() handler.