Re: [PATCH 7/7] t: invert `GIT_TEST_WRITE_REV_INDEX`

[Derrick Stolee <derrickstolee@github.com>]

On 4/11/2023 5:33 PM, Taylor Blau wrote:
> On Tue, Apr 11, 2023 at 09:51:06AM -0400, Derrick Stolee wrote:
>> On 4/10/2023 6:53 PM, Taylor Blau wrote:
>>> Instead of getting rid of the option, invert its meaning to instead
>>> disable writing ".rev" files, thereby running the test suite in a mode
>>> where the reverse index is generated from scratch.
>>>
>>> This ensures that we are still running and exercising Git's behavior
>>> when forced to generate reverse indexes from scratch.
>>
>> I don't think this is true because you remove the environment
>> variable from the following test.
> 
> This is intentional; I wrote that last sentence ("This ensures...") with
> an implied "[When set], this ensures..." at the beginning of it. IOW, if
> you wanted to run the test suite with primarily in-memory reverse
> indexes, you still could.

I guess I think of "we are still running and exercising" as only
being true if it happens during regular CI, not just when someone
thinks to try it.

> I wasn't quite sure what to do here. On one hand, sticking
> GIT_TEST_NO_WRITE_REV_INDEX=1 here would ensure that the linux-TEST-vars
> test is still exercising the old code.
> 
> Is that desirable? I dunno. On one hand it increases our coverage, but
> on the other hand I've always treated this suite as for experimental
> features, not older ones.
> 
> But I think all things being equal, I'd rather have more CI coverage
> than not, so I'll add it back in. Thanks for a sanity check on this one.

If we think there is value in continuing to test the case without .rev
files by default, then adding it in would be good. I think it has some
value at least for some time after the transition. We're unlikely to
remember to remove it, but having the extra mode in this build is not
too much overhead.

We should consider auditing this build just to be sure we want to
continue testing these options or if some could be removed in favor
of new defaults.

Thanks,
-Stolee