Re: [PATCH v5 4/4] environment: move has_symlinks into repo_config_values

[Junio C Hamano <gitster@pobox.com>]

Tian Yuchen <cat@malon.dev> writes:

> Note:
> To support early platform-specific (MinGW) overrides
> before repository initialization, a global variable
> 'default_has_symlinks' fallback is introduced as a fallback
> in environment.h. The *writer* in compat/mingw.c can only
> access this variable.

This may invite people to abuse the global variable.  I wonder if we
want to do something similar to how we handle is_dir_sep() and
friends instead.

The idea is to have something like this in the generic header:

        #ifndef platform_has_symlinks
        #define platform_has_symlinks() 1
        #endif

And then allow selected platforms override it:

        /* in compat/mingw.h */
        #define platform_has_symlinks() mingw_platform_has_symlinks()
        extern int mingw_platform_has_symlinks(void);

        /* in compat/mingw.c */
        int mingw_platform_has_symlinks(void)
        {
                if (!(tmp = getenv("MSYS")) || !strstr(tmp, "winsymlinks:nativestrict"))
                        return 0;
                else
                        return 1;
        }

This keeps the namespace clean and avoids exposing a mutable state
variable that others might be tempted to meddle with.