Feature/git error hint

[jhf]

Provide a hint for the user to run a cleanup to avoid the errors in #709 if the package state is corrupt for some reason.

Preparation to provoke the error (on macOS):

mint install
rm -rf $TMPDIR/mint-packages/https:/github.com/mint-lang/mint-ui.git/.git/*

The old behaviour - without a hint:

mint install
Mint - Installing dependencies
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
⚙ Constructing dependency tree...

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

░ ERROR (REPOSITORY_COULD_NOT_UPDATE) ░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░

I could not update the repository: https://github.com/mint-lang/mint-ui.git

The error I got from the git command is this:

fatal: not a git repository (or any of the parent directories): .git

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
There was an error, exiting...

The new behaviour - with a hint:

mint install
Mint - Installing dependencies
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
⚙ Constructing dependency tree...

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

░ ERROR (REPOSITORY_COULD_NOT_UPDATE) ░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░

I could not update the repository: https://github.com/mint-lang/mint-ui.git

The error I got from the git command is this:

fatal: not a git repository (or any of the parent directories): .git

Hint: Run  mint tool clean; mint tool clean --package-cache  to reset local
state, and then try again.

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
There was an error, exiting...

[Sija]

Extraneous space here.

ditto elsewhere