Support --parallel auto option

[StephanKuempel]

Currently, when specifiying sphinx-performance --parallel auto (equivalent sphinx-build -j auto) we get the error:
Error: Invalid value for '--parallel': 'auto' is not a valid integer.

[danwos]

Thanks for the reports, but I'm not sure if a performance-report script should provide a non reproducible option, which may interact differently on each machine.

Also "auto" would currently not get resolved in the report and you would have no glue, how many cpu cores got used for a specific report.

For me "auto" makes only sense, if you don't know the available cores on a system. But then I don't know, if a created report is comparable to any other report....

[StephanKuempel]

Ok, makes sense, thne maybe just add to the doku, that with --parallel, the auto option is not supported like it is for -j in sphinx-build.
The -j option itself is not very good, since you never know if the number you specified is really supported/used, since sphinx limits itself internally if too big, so you'll never know for sure how many cores were used ;)

[danwos]

Thanks for the hint with -j.
Maybe in this case sphinx-performance should also do a check and write a warning, if not so many cores are available as specified.

[StephanKuempel]

Thanks for the hint with -j. Maybe in this case sphinx-performance should also do a check and write a warning, if not so many cores are available as specified.

Then sphinx-performance would be better than sphinx-build, actually ;)
As a side note: -j option doesn't work at all on Windows. Parallel is simply not supported, but sphinx-build doesn't give any info on that ...