From: Lutz Lengemann <lutz@lengemann.net>

The zsh completion wrapper (__git_zsh_main) did not handle the global -C
option, so "git -C <path> <command> <TAB>" offered nothing and could not
complete a command's arguments.

Three things are needed to make it work, all scoped to -C:

  - Add -C to the _arguments specification, so completion no longer stops
    at it.

  - Advance __git_cmd_idx past any leading "-C <path>" options. The index
    is hard-coded to 1, i.e. the command is assumed to be the first
    argument; with -C present the command sits two words later for each
    -C, so the bash helpers otherwise look at the wrong word and produce
    nothing.

  - Collect the -C paths into __git_C_args, as __git_main does. The bash
    helpers run git to resolve aliases and list refs; without the -C
    paths they run in the current directory, so completion fails whenever
    the cwd is not the target repository or the command is an alias.

With these, "git -C <path> <command> <TAB>" completes the command, its
options and its arguments, including outside the repository, through
aliases, and with repeated -C options.

Signed-off-by: Lutz Lengemann <lutz@lengemann.net>

Submitted-As: https://lore.kernel.org/git/pull.2155.git.1781710256081.gitgitgadget@gmail.com