Re: [PATCH v4 1/1] Make gitdir work with worktrees, respect core.hooksPath, etc

From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Pratyush Yadav <me@yadavpratyush.com>
Cc: Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, Bert Wesarg <bert.wesarg@googlemail.com>
Subject: Re: [PATCH v4 1/1] Make gitdir work with worktrees, respect core.hooksPath, etc
Date: Sat, 12 Oct 2019 23:24:12 +0200 (CEST)	[thread overview]
Message-ID: <nycvar.QRO.7.76.6.1910122321211.3272@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <20191011222611.le5lyf6mr5lmvbbd@yadavpratyush.com>

Hi Pratyush,

On Sat, 12 Oct 2019, Pratyush Yadav wrote:

> On 08/10/19 04:33AM, Johannes Schindelin via GitGitGadget wrote:
>
> > @@ -1453,10 +1501,16 @@ proc rescan {after {honor_trustmtime 1}} {
> >  	global HEAD PARENT MERGE_HEAD commit_type
> >  	global ui_index ui_workdir ui_comm
> >  	global rescan_active file_states
> > -	global repo_config
> > +	global repo_config _gitdir_cache
> >
> >  	if {$rescan_active > 0 || ![lock_index read]} return
> >
> > +	# Only re-prime gitdir cache on a full rescan
> > +	if {$after ne "ui_ready"} {
>
> What do you mean by a "full rescan"? I assume you use it as the
> differentiator between `ui_do_rescan` (called when you hit F5 or choose
> rescan from the menu) and `do_rescan` (called when you revert a line or
> hunk), and a "full rescan" refers to `ui_do_rescan`.
>
> Well in that case, this check is incorrect. `do_rescan` passes only
> "ui_ready" and `ui_do_rescan` passes "force_first_diff ui_ready".
>
> But either way, I'm not a big fan of this. This check makes assumptions
> about the behaviour of its callers based on what they pass to $after.
> The way I see it, $after should be a black box to `rescan`, and it
> should make absolutely no assumptions about it.
>
> Doing it this way is really brittle, and would break as soon as someone
> changes the behaviour of `ui_do_rescan`. If someone in the future passes
> a different value in $after, this would stop working as intended and
> would not refresh the cached list on a rescan.
>
> So, I think a better place for this if statement would be in
> `ui_do_rescan`. This would mean adding a new function that does this.
> But if we unset _gitdir_cache in prime_gitdir_cache (I see no reason not
> to), we can get away with just something like:
>
>   proc ui_do_rescan {} {
>   	rescan {prime_gitdir_cache; ui_ready}
>   }
>
> Though since `prime_gitdir_cache` does not really depend on the rescan
> being finished, something like this would also work fine:
>
>   proc ui_do_rescan {} {
>   	rescan ui_ready
>   	prime_gitdir_cache
>   }

That was my first attempt. However, there is a very important piece of
code that is even still quoted above: that `if {$rescan_active > 0 ||
![lock_index read]} return` part.

I do _not_ want to interfere with an actively-going-on rescan. If there
is an active one, I don't want to re-prime the `_gitdir` cache.

That was the reason why I put the additional code into `rescan` rather
than into `ui_do_rescan()`.

Ciao,
Johannes

>
> This would allow us to do these two things in parallel since `rescan` is
> asynchronous. But that would also mean it is possible that the status
> bar would show "Ready" while `prime_gitdir_cache` is still executing.
>
> I can't really make up my mind on what is better. I'm inclining on using
> the latter way, effectively trading a bit of UI inconsistency for
> performance (at least in theory).
>
> Thoughts?
>
> > +		array unset _gitdir_cache
> > +		prime_gitdir_cache
> > +	}
> > +
> >  	repository_state newType newHEAD newMERGE_HEAD
> >  	if {[string match amend* $commit_type]
> >  		&& $newType eq {normal}
>
> --
> Regards,
> Pratyush Yadav
>