Can't use -c in fetch and pull

[marcosboggia]

Using the current API I'm not able to use -c configurations when I use fetch and pull.
For example:

...> Git.fetch(repo, ["-c", "credential.helper="])
...> {:error,
 %Git.Error{
   message: "error: unknown switch `c'\nusage: git fetch [<options>] [<repository> [<refspec>...]]\n   or: git fetch [<options>] <group>\n   or: git fetch --multiple [<options>] [(<repository> | <group>)...]\n   or: git fetch --all [<options>]\n\n    -v, --[no-]verbose    be more verbose\n    -q, --[no-]quiet      be more quiet\n    --[no-]all            fetch from all remotes\n    --[no-]set-upstream   set upstream for git pull/fetch\n    -a, --[no-]append     append to .git/FETCH_HEAD instead of overwriting\n    --[no-]atomic         use atomic transaction to update references\n    --[no-]upload-pack <path>\n                          path to upload pack on remote end\n    -f, --[no-]force      force overwrite of local reference\n    -m, --[no-]multiple   fetch from multiple remotes\n    -t, --[no-]tags       fetch all tags and associated objects\n    -n                    do not fetch all tags (--no-tags)\n    -j, --[no-]jobs <n>   number of submodules fetched in parallel\n    --[no-]prefetch       modify the refspec to place all refs within refs/prefetch/\n    -p, --[no-]prune      prune remote-tracking branches no longer on remote\n    -P, --[no-]prune-tags prune local tags no longer on remote and clobber changed tags\n    --[no-]recurse-submodules[=<on-demand>]\n                          control recursive fetching of submodules\n    --[no-]dry-run        dry run\n    --[no-]porcelain      machine-readable output\n    --[no-]write-fetch-head\n                          write fetched references to the FETCH_HEAD file\n    -k, --[no-]keep       keep downloaded pack\n    -u, --[no-]update-head-ok\n                          allow updating of HEAD ref\n    --[no-]progress       force progress reporting\n    --[no-]depth <depth>  deepen history of shallow clone\n    --[no-]shallow-since <time>\n                          deepen history of shallow repository based on time\n    --[no-]shallow-exclude <revision>\n                          deepen history of shallow clone, excluding rev\n    --[no-]deepen <n>     deepen history of shallow clone\n    --unshallow           convert to a complete repository\n    --refetch             re-fetch without negotiating common commits\n    --[no-]update-shallow accept refs that update .git/shallow\n    --refmap <refmap>     specify fetch refmap\n    -o, --[no-]server-option <server-specific>\n                          option to transmit\n    -4, --ipv4            use IPv4 addresses only\n    -6, --ipv6            use IPv6 addresses only\n    --[no-]negotiation-tip <revision>\n                          report that we have only objects reachable from this object\n    --[no-]negotiate-only do not fetch a packfile; instead, print ancestors of negotiation tips\n    --[no-]filter <args>  object filtering\n    --[no-]auto-maintenance\n                          run 'maintenance --auto' after fetching\n    --[no-]auto-gc        run 'maintenance --auto' after fetching\n    --[no-]show-forced-updates\n                          check for forced-updates on all updated branches\n    --[no-]write-commit-graph\n                          write the commit-graph after fetching\n    --[no-]stdin          accept refspecs from stdin\n\n",
   command: "fetch",
   code: 129,
   args: ["-c", "credential.helper="]
 }}

This does not happen with clone:

...> Git.clone(["-c", "credential.helper=", "https://github.com/marcosboggia/testingrepo.git", "/tmp/a"])
...> {:ok, %Git.Repository{path: "/tmp/a"}}

I can see that, using git in the terminal, this is valid:
git -c credential.helper= fetch origin ✅
and this returns the same error as described at beginning of this issue:
git fetch -c credential.helper= origin ❌

It seems that git-cli is generating the latter command which does't work. Maybe there is a way to add dynamically the configs in the correct place

From man git it seems that there are two types of arguments to take in account: git arguments and command arguments:

SYNOPSIS
       git [-v | --version] [-h | --help] [-C <path>] [-c <name>=<value>]
           [--exec-path[=<path>]] [--html-path] [--man-path] [--info-path]
           [-p|--paginate|-P|--no-pager] [--no-replace-objects] [--bare]
           [--git-dir=<path>] [--work-tree=<path>] [--namespace=<name>]
           [--config-env=<name>=<envvar>] <command> [<args>]
           
One last thing to consider, git clone arguments supports --config; git fetch doesn't:
https://git-scm.com/docs/git-clone#Documentation/git-clone.txt-code--configcodeemltkeygtemcodecodeemltvaluegtem
But --config not found in:
https://www.git-scm.com/docs/git-fetch