Wrong or incomplete error message when using non-bors git commit as --start

[jruderman]

$ cargo-bisect-rustc --preserve --start=e67f09ac799e4a6e4e90147d62c94c9ddcc94197 --end=7aa361390867181d225a7775340f50e8162e16a2
bisecting ci builds
starting at e67f09ac799e4a6e4e90147d62c94c9ddcc94197, ending at 7aa361390867181d225a7775340f50e8162e16a2
opening existing repository at "rust.git"
Found origin remote under name `origin`
refreshing repository at "rust.git"
remote: Enumerating objects: 209, done.
remote: Counting objects: 100% (180/180), done.
remote: Compressing objects: 100% (53/53), done.
remote: Total 209 (delta 148), reused 140 (delta 127), pack-reused 29
Receiving objects: 100% (209/209), 165.35 KiB | 2.71 MiB/s, done.
Resolving deltas: 100% (149/149), completed with 88 local objects.
From https://github.com/rust-lang/rust
   7aa36139086..7feb003882e  master     -> origin/master
fetching (via local git) commits from e67f09ac799e4a6e4e90147d62c94c9ddcc94197 to 7aa361390867181d225a7775340f50e8162e16a2
opening existing repository at "rust.git"
Found origin remote under name `origin`
refreshing repository at "rust.git"
looking up first commit
looking up second commit
checking that commits are by bors and thus have ci artifacts...
ERROR: failed during attempt to create/access local git repository

It should say what problem it caused the bisector to exit: a non-bors commit was specified as start.

(Or it could guess some appropriate bors commit to use in place of the one I specified.)

Version

cargo-bisect-rustc --version
cargo-bisect-rustc 0.6.4

on mac

[ngc0202]

I just spent too long debugging the same exact issue. The issue is in main they're Display printing the error, which shows the minimal amount of info instead of pretty-printing or Debug printing which shows the complete cause.

[ehuss]

I think that between #103 and #237, this is resolved.

However, there is an issue with github access that causes it to panic. I have opened #318 to fix that.