There are several strategies to manage this, I will outline two of them here.

Using Conditional Includes in Git Configuration

For the past few years, a colleague of mine introduced me to the concept of conditional includes in Git configuration.

[user]
	name = Your Name
	email =	personal@email.com

[includeIf "gitdir:~/work/"]
	path = ~/.gitconfig-work

In this setup, the main Git configuration file (~/.gitconfig) contains your default user information, which applies to personal projects. The includeIf directive checks if the Git directory is within the ~/work/ path and includes the additional configuration file (~/.gitconfig-work), which contains your work-specific settings.

This approach is solid and works very well and is battle-tested.

Using cd hooks for Dynamic Configuration

Because I work on multiple projects, each requiring different Git configurations, I needed a more dynamic solution. I wanted to automatically apply the correct Git configuration based on the current working directory (or rather the nearest .gitconfig file in the directory tree).

Popularized by tools like direnv, asdf, and others, using cd hooks allows you to run custom scripts whenever you change directories.

This is perfect for my use case, and the idea is simple:

1. When changing directories, search upwards in the directory tree for the nearest .gitconfig file.
2. If found, merge it with the global Git configuration for the current session using GIT_CONFIG_GLOBAL.
3. If no .gitconfig is found, revert to the default global configuration.

And I just did that for Bash, Zsh and PowerShell which are the shells I use the most.

<details data-group="shell-config" open> <summary>Bash</summary>

merge_nearest_gitconfig() {
    # Reset any previous temporary git config
	# so if we cd out of a project with a .gitconfig we go back to normal
    if [[ -n "$GIT_CONFIG_GLOBAL" ]]; then
        rm -f "$GIT_CONFIG_GLOBAL" 2>/dev/null
        unset GIT_CONFIG_GLOBAL
    fi

    local current_dir="$PWD"
    local nearest_gitconfig=""

    # Find the nearest .gitconfig file upwards in the directory tree
    while [[ -n "$current_dir" ]]; do
        local gitconfig_path="$current_dir/.gitconfig"
        if [[ -f "$gitconfig_path" ]]; then
            nearest_gitconfig="$gitconfig_path"
            break
        fi

        # Move up one directory
        current_dir="${current_dir%/*}"
    done

    # if the found .gitconfig is not the same as user's global config, merge it
    if [[ -n "$nearest_gitconfig" && "$nearest_gitconfig" != "$HOME/.gitconfig" ]]; then
        # Create a temporary config file with the user's global config ~/.gitconfig
        local temp_config=$(mktemp)
        cat "$HOME/.gitconfig" > "$temp_config"

        # Append an include directive for the nearest .gitconfig
        echo -e "\n[include]\n    path = $nearest_gitconfig" >> "$temp_config"

        # Point Git to this merged config for the session
        export GIT_CONFIG_GLOBAL="$temp_config"
        echo "Merged git config from \e[36m$nearest_gitconfig\e[0m into current session."
    fi

}

# Function to change directory and immediately merge neatest git config
_cd_with_nearest_git() {
	\cd "$@" || return $?
	merge_nearest_gitconfig
}


alias cd='_cd_with_nearest_git'  # Override cd to our custom function
merge_nearest_gitconfig          # Run it once for the initial directory

</details>

<details data-group="shell-config"> <summary>Zsh</summary>

merge_nearest_gitconfig() {
    # Reset any previous temporary git config
	# so if we cd out of a project with a .gitconfig we go back to normal
    if [[ -n "$GIT_CONFIG_GLOBAL" ]]; then
        rm -f "$GIT_CONFIG_GLOBAL" 2>/dev/null
        unset GIT_CONFIG_GLOBAL
    fi

    local current_dir="$PWD"
    local nearest_gitconfig=""

    # Find the nearest .gitconfig file upwards in the directory tree
    while [[ -n "$current_dir" ]]; do
        local gitconfig_path="$current_dir/.gitconfig"
        if [[ -f "$gitconfig_path" ]]; then
            nearest_gitconfig="$gitconfig_path"
            break
        fi

        # Move up one directory
        current_dir="${current_dir%/*}"
    done

    # if the found .gitconfig is not the same as user's global config, merge it
    if [[ -n "$nearest_gitconfig" && "$nearest_gitconfig" != "$HOME/.gitconfig" ]]; then
        # Create a temporary config file with the user's global config ~/.gitconfig
        local temp_config=$(mktemp)
        cat "$HOME/.gitconfig" > "$temp_config"

        # Append an include directive for the nearest .gitconfig
        echo -e "\n[include]\n    path = $nearest_gitconfig" >> "$temp_config"

        # Point Git to this merged config for the session
        export GIT_CONFIG_GLOBAL="$temp_config"
        echo "Merged git config from \e[36m$nearest_gitconfig\e[0m into current session."
    fi

}

autoload -U add-zsh-hook                   # load the add-zsh-hook function
add-zsh-hook chpwd merge_nearest_gitconfig # Run it on directory change
merge_nearest_gitconfig                    # Run it once for the initial directory

</details>

<details data-group="shell-config"> <summary>PowerShell</summary>

Function Merge-NearestGitConfig {
    # Reset any previous temporary git config
    if ($Env:GIT_CONFIG_GLOBAL) {
        Remove-Item $Env:GIT_CONFIG_GLOBAL -ErrorAction SilentlyContinue
        Remove-Item Env:GIT_CONFIG_GLOBAL
    }

    $currentDir = Get-Location
    $nearestGitconfig = $null

    # Find the nearest .gitconfig file upwards in the directory tree
    while ($currentDir) {
        $gitconfigPath = Join-Path -Path $currentDir -ChildPath ".gitconfig"
        if (Test-Path $gitconfigPath) {
            $nearestGitconfig = $gitconfigPath
            break
        }

        # Move up one directory
        $currentDir = Split-Path -Path $currentDir -Parent
    }

    # if the found .gitconfig is not the user's global config, merge it
    if ($nearestGitconfig -and ($nearestGitconfig -ne "$HOME\.gitconfig")) {
        # Create a temporary config file with the user's global config ~/.gitconfig
        $tempConfig = [System.IO.Path]::GetTempFileName()
        Get-Content "$HOME\.gitconfig" | Set-Content $tempConfig

        # Append an include directive for the nearest .gitconfig
        $nearestGitconfig = $nearestGitconfig -replace '\\', '/' # Normalize path for git
        Add-Content $tempConfig "`n[include]`n    path = $nearestGitconfig"

        # Point Git to this merged config for the session
        $Env:GIT_CONFIG_GLOBAL = $tempConfig
        Write-Host "Merged git config from " -NoNewline
        Write-Host $nearestGitconfig -NoNewline -ForegroundColor Cyan
        Write-Host " into current session."
    }
}

# Function to change directory and immediately merge neatest git config
Function __cd_with_nearest_git {
	Set-Location @args
	Merge-NearestGitConfig
}

Remove-Alias cd -ErrorAction SilentlyContinue             # Remove existing cd
Set-Alias cd __cd_with_nearest_git -Scope Global -Force   # Override cd to our custom function
Merge-NearestGitConfig                                    # Run it once for the initial directory

</details>

This way I can have the following structure:

~/
├── .gitconfig
├── work/
│   ├── .gitconfig
│   └── project-a/
└── work2/
│   ├── .gitconfig
│   ├── project-b/
│   └── project-c/

~/.gitconfig would contain my default personal settings, while each work-related directory contains its own .gitconfig file with the appropriate user information.