I have created a custom Git command called git-profile. It uses the git-<command> naming convention to enable use as compword in Git Bash completion. implemented as a Bash script, that accepts a command line of the form:

git profile PROFILE_NAME [git-opts]

where git-opts is any valid sequence of Git command line options with respective arguments. The use case of this command is simply to set GIT_CONFIG_GLOBAL for the current invocation.

I’m trying to get Bash completion working with this command such that, starting with the third command line word, the chain of available COMPREPLYs is sourced directly from Git’s default completion. (In my installation, that’s the completion script included in GitHub’s contrib tree [cf. GitHub]).

I have passthrough completion working, with the caveat that subsequent COMPREPLYs contain appropriate choice sets, but they are never autocompleted, even for partial matches. For any input after PROFILE_NAME, I only get a subsequent option or arg’s set of compwords if I type the entire prior arg and press SPACE.

Here’s the full completion script. (Note that the shebang is included as a temp workaround to enable LSP settings in my IDE; including here for the sake of high fidelity.)

#!/bin/bash

source /usr/share/bash-completion/completions/git

shopt -s nullglob

__git_profile_word_in() {
  local _needle="$1"
  local _haystack="${*:2}"

  # Disable checking for regex matching syntax
  # This is a deliberate literal match test
  # shellcheck disable=SC2076
  [[ " ${_haystack} " =~ " ${_needle} " ]]
}

__git_profile_get_profiles() {
  local cur="$1"
  local -r profiles_dir="$2"
  local -a profiles=()

  for profile_dir in "${profiles_dir%/}/$cur"*; do
    profiles+=("${profile_dir##*/}")
  done

  echo "${profiles[@]}"
}

_git_profile() {
  local -r _cur="${COMP_WORDS[COMP_CWORD]}"
  local profiles_dir="${GIT_PROFILE_CONFIG_HOME:-${HOME}/.config/git/profiles}"
  local profile

  local -ar profiles=("$(__git_profile_get_profiles "$_cur" "$profiles_dir")")
  local -ar word_opts=("${profiles[@]}" 'add')

  case $COMP_CWORD in
  0 | 1)
    return
    ;;
  2)
    __gitcomp "${word_opts[*]}"
    return
    ;;
  *)
    local -r profile_cmd_arg=${COMP_WORDS[2]}

    if [[ "$profile_cmd_arg" == 'add' ]]; then
      # git-profile subcommand - takes no args
      return
    fi

    if ! __git_profile_word_in "$profile_cmd_arg" "${profiles[@]}"; then
      # Unsupported scenario
      return
    fi

    profile="${profiles_dir}/${profile_cmd_arg}/config"
    ;;
  esac

  local -r OLD_COMP_SUBSTR="${COMP_WORDS[*]:1:2}"
  local -r COMP_WORDS_REBUILT=('git' "${COMP_WORDS[@]:3}")

  # Forward a Git command line without the `profile` option and arg so that we
  # can take advantage of completion for all available commands
  # Note that we substract the trailing space from COMP_POINT
  # to prevent displacing the completion cursor
  COMP_WORDS=("${COMP_WORDS_REBUILT[@]}")
  COMP_LINE="${COMP_WORDS_REBUILT[*]}"
  COMP_CWORD=$((COMP_CWORD - 2))
  COMP_POINT=$((COMP_POINT - ${#OLD_COMP_SUBSTR} - 1))

  GIT_CONFIG_GLOBAL="$profile" __git_func_wrap __git_main
}

The last block before the call to __git_func_wrap, strips the command line of words specific to git-profile and resets the corresponding indexes as if those words were never part of the original command line. I then forward this newly stripped command line to the Git-provided completion script with the configured global config (this is probably not necessarily useful atm, but I’m also working on a separate extension to allow reading in custom [/non-“Git-native”] settings from the current config). I’m confident that this is a viable approach as I’ve had success wrapping completion routines for similar wrapper/extension scripts that I’ve written, such as for pass, and they notably don’t exhibit the unexpected behavior described below.

If I type git profile projs and press the TAB key twice, I get the following COMPREPLY:

add               describe          mergetool         revert
am                diff              mv                rm
apply             difftool          notes             scalar
archive           fetch             profile           send-email
bisect            flow              prune             shortlog
blame             format-patch      pull              show
branch            fsck              push              show-branch
bundle            gc                range-diff        sparse-checkout
checkout          gitk              rebase            stage
cherry            grep              reflog            stash
cherry-pick       gui               remote            status
citool            help              remote-bzr        submodule
clang-format      init              repack            switch
clean             instaweb          replace           tag
clone             log               request-pull      whatchanged
commit            maintenance       reset             worktree
config            merge             restore

If I type git profile projs r and press the TAB key twice, I get an empty COMPREPLY. This continues as I type additional letters until I have the full word remote on the command line and before I press SPACE.

If I type git profile projs remote (note the final space) and press the TAB key twice, I get the following COMPREPLY:

add            prune          rename         set-head       show 
get-url        remove         set-branches   set-url        update 

I’m struggling to understand the Git-provided completion script, so my attempts around this have not been particularly systematic (my confusion starts roughly after chasing references down to _get_comp_words_by_ref, but most of the functions resolved for refs seem to be utilized by command-specific completion routines). I’ve tried looking for an entry point that allows me to pass in the current compword directly – the fact that I’m getting the right compreplies leads me to think that the completion script somehow isn’t aware of the current compword, but AFAICT I’ve modulated the cursor/COMP_POINT correctly. What am I missing to enable TAB-triggered COMPREPLYs for partial word matches?

I’d appreciate any insight in the right direction.