Bug: branch checkout is detached if the case doesn't match

[Tim Hutt <tdhutt@xxxxxxxxx>]

If you try to switch to a branch (e.g. `master`), but get the case wrong, e.g:

    git switch MASTER
    git checkout MASTER
    git switch Master
    git checkout Master

etc. then it autocorrects the case (bad idea but ok), but it also
enables the `--detach` flag! In other words

    git switch Master

acts like

    git switch -d master

Very unexpected!

Cheers,

Tim

[System Info]
git version:
git version 2.32.0
cpu: x86_64
no commit associated with this build
sizeof-long: 8
sizeof-size_t: 8
shell-path: /bin/sh
uname: Darwin 20.4.0 Darwin Kernel Version 20.4.0: Fri Mar  5 01:14:14
PST 2021; root:xnu-7195.101.1~3/RELEASE_X86_64 x86_64
compiler info: clang: 12.0.5 (clang-1205.0.22.9)
libc info: no libc information available
$SHELL (typically, interactive shell): /bin/zsh

[Enabled Hooks]