Re: [PATCH v6 3/3] exec_cmd: RUNTIME_PREFIX on some POSIX systems

> Enable Git to resolve its own binary location using a variety of
> OS-specific and generic methods, including:
>
> - procfs via "/proc/self/exe" (Linux)
> - _NSGetExecutablePath (Darwin)
> - KERN_PROC_PATHNAME sysctl on BSDs.
> - argv0, if absolute (all, including Windows).
>
> This is used to enable RUNTIME_PREFIX support for non-Windows systems,
> notably Linux and Darwin. When configured with RUNTIME_PREFIX, Git will
> do a best-effort resolution of its executable path and automatically use
> this as its "exec_path" for relative helper and data lookups, unless
> explicitly overridden.
>
> Small incidental formatting cleanup of "exec_cmd.c".
>
> Signed-off-by: Dan Jacques <dnj@google.com>
> Thanks-to: Robbie Iannucci <iannucci@google.com>
> Thanks-to: Junio C Hamano <gitster@pobox.com>
> ---

> diff --git a/Makefile b/Makefile
> index 101a98a78..df17a62a4 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -418,6 +418,16 @@ all::
>  #
>  # Define HAVE_BSD_SYSCTL if your platform has a BSD-compatible sysctl function.
>  #
> +# Define HAVE_BSD_KERN_PROC_SYSCTL if your platform supports the KERN_PROC BSD
> +# sysctl function.
> +#
> +# Define PROCFS_EXECUTABLE_PATH if your platform mounts a "procfs" filesystem
> +# capable of resolving the path of the current executable. If defined, this
> +# must be the canonical path for the "procfs" current executable path.
> +#
> +# Define HAVE_NS_GET_EXECUTABLE_PATH if your platform supports calling
> +# _NSGetExecutablePath to retrieve the path of the running executable.
> +#

> +/**
> + * Path to the current Git executable. Resolved on startup by
> + * 'git_resolve_executable_dir'.
> + */
> +static const char *executable_dirname;
>  
>  static const char *system_prefix(void)
>  {
>  	static const char *prefix;
>  
> -	assert(argv0_path);
> -	assert(is_absolute_path(argv0_path));
> +	assert(executable_dirname);
> +	assert(is_absolute_path(executable_dirname));
>  
>  	if (!prefix &&
> -	    !(prefix = strip_path_suffix(argv0_path, GIT_EXEC_PATH)) &&
> -	    !(prefix = strip_path_suffix(argv0_path, BINDIR)) &&
> -	    !(prefix = strip_path_suffix(argv0_path, "git"))) {
> +	    !(prefix = strip_path_suffix(executable_dirname, GIT_EXEC_PATH)) &&
> +	    !(prefix = strip_path_suffix(executable_dirname, BINDIR)) &&
> +	    !(prefix = strip_path_suffix(executable_dirname, "git"))) {
>  		prefix = PREFIX;
>  		trace_printf("RUNTIME_PREFIX requested, "
> -				"but prefix computation failed.  "
> -				"Using static fallback '%s'.\n", prefix);
> +			     "but prefix computation failed.  "
> +			     "Using static fallback '%s'.\n",
> +			     prefix);
>  	}
>  	return prefix;
>  }