Re: Automatic (e)tags generation and incremental updates

[Tom Tromey]

Thank you for CCing me on this.

Dmitry> - Call some xref command like 'M-.'. See message "Generating new tags
Dmitry>   table..." (it's saved in /tmp/...), then see navigation happen.

On "xdg"-ish systems, it would make sense to use the XDG cache directory
here.

Dmitry> - Pressing C-M-i instead should also trigger tags table generation.

Dmitry> - When you switch between projects, the previously generated tags
Dmitry>   tables are discarded. It's not too hard to improve, but that would
Dmitry>  involve some choices/tradeoffs.

What are the tradeoffs?

I tend to think that conceptually each buffer should point to its
corresponding tags table.  Then some separate logic could be used to
decide when to kill some tag file buffer.

Dmitry> - When files are deleted, or otherwise changed outside of Emacs
Dmitry>   (perhaps with 'git checkout'), nothing is updated. I have a few new
Dmitry>  ideas, haven't started on them yet. Workaround: toggle
Dmitry> etags-regen-mode off and on, which will result in full rescan when you
Dmitry> use 'M-.'.

It seems to me that the default ought to be to update the tags table on M-.
One nice way to do this would be to run etags in the background, so that
the work of updating would be done in parallel with the user typing,
since presumably you'd want to ensure that etags has finished before
jumping to the result (or fulfilling a completion request).

Tom