Nightly can be checked thrice in certain cases

[hellow554]

$ cargo-bisect-rustc --end=2020-05-09
installing nightly-2020-05-09
RESULT: nightly-2020-05-09, ===> Yes
uninstalling nightly-2020-05-09

installing nightly-2020-05-07
RESULT: nightly-2020-05-07, ===> Yes
uninstalling nightly-2020-05-07

installing nightly-2020-05-05
RESULT: nightly-2020-05-05, ===> Yes
uninstalling nightly-2020-05-05

installing nightly-2020-05-03
RESULT: nightly-2020-05-03, ===> No
uninstalling nightly-2020-05-03

installing nightly-2020-05-05
RESULT: nightly-2020-05-05, ===> Yes
uninstalling nightly-2020-05-05

installing nightly-2020-05-04
RESULT: nightly-2020-05-04, ===> No
uninstalling nightly-2020-05-04

searched toolchains nightly-2020-05-03 through nightly-2020-05-05
installing nightly-2020-05-05
uninstalling nightly-2020-05-05


********************************************************************************
Regression in nightly-2020-05-05
********************************************************************************

As you can see, 2020-05-05 is downloaded and tested thrice. Is that necessary?

[spastorino]

I've noticed this and it's one of the things that should be fixed :).

[chrissimpkins]

I always run with start and end dates and have not seen many of these recent issues with end only runs. We need to look into that area of the source.

[chrissimpkins]

I suggest that we look into the skip intervals when we investigate this. I sense that we may be adding far too many steps to find the first non-fail date before the bisection starts in an average case situation. I wonder if it is faster to initially step back by, say, one month and begin there?

[hellow554]

Funny enough this still isn't fixed as of today:

installing nightly-2020-12-08
std for x86_64-unknown-linux-gnu: 24.58 MB / 24.58 MB [================================================================================] 100.00 % 5.77 MB/s testing...
RESULT: nightly-2020-12-08, ===> Yes
uninstalling nightly-2020-12-08

installing nightly-2020-12-01
std for x86_64-unknown-linux-gnu: 24.52 MB / 24.52 MB [================================================================================] 100.00 % 5.49 MB/s testing...
RESULT: nightly-2020-12-01, ===> No
uninstalling nightly-2020-12-01

installing nightly-2020-12-08
std for x86_64-unknown-linux-gnu: 24.58 MB / 24.58 MB [================================================================================] 100.00 % 6.96 MB/s testing...
RESULT: nightly-2020-12-08, ===> Yes
uninstalling nightly-2020-12-08

Would it be would it be feasible to save the tested toolchains together with a status in a hashmap or similar?

[hellow554]

The even happens, when your start and end date are next to each other:

 cargo-bisect-rustc --start 2020-10-26 --end 2020-10-27

installing nightly-2020-10-26
RESULT: nightly-2020-10-26, ===> No
uninstalling nightly-2020-10-26

installing nightly-2020-10-27
RESULT: nightly-2020-10-27, ===> Yes
uninstalling nightly-2020-10-27

searched toolchains nightly-2020-10-26 through nightly-2020-10-27
installing nightly-2020-10-27
uninstalling nightly-2020-10-27