Support locally modified repos

[SebastienGardoll]

Modify or update a repos in .cache, then:

rye run esgvoc install                                                                                                                                                 
fatal: destination path '.cache/repos/CMIP6Plus_CVs' already exists and is not an empty directory.
Already up to date.

[SebastienGardoll]

The same error message appends when the repos is updated. It doesn't seem to prevent the update, but it is scary for sure.

 rye run esgvoc install                                                                                                                                                  [16:24:32]
fatal: destination path '.cache/repos/CMIP6Plus_CVs' already exists and is not an empty directory.
remote: Enumerating objects: 16, done.
remote: Counting objects: 100% (16/16), done.
remote: Compressing objects: 100% (14/14), done.
remote: Total 16 (delta 4), reused 6 (delta 2), pack-reused 0 (from 0)
Unpacking objects: 100% (16/16), 4.37 KiB | 279.00 KiB/s, done.
From https://github.com/ESPRI-Mod/CMIP6Plus_CVs
   40c5f60..160e616  uni_proj_ld -> origin/uni_proj_ld
   60a44b6..abc1d40  main        -> origin/main
Updating 40c5f60..160e616
Fast-forward
 project_specs.json | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)