Re: [PATCH bw/realpath-wo-chdir] real_path: canonicalize directory separators in root parts

> When an absolute path is resolved, resolution begins at the first path
> component after the root part. The root part is just copied verbatim,
> because it must not be inspected for symbolic links. For POSIX paths,
> this is just the initial slash, but on Windows, the root part has the
> forms c:\ or \\server\share. We do want to canonicalize the back-slashes
> in the root part because these parts are compared to the result of
> getcwd(), which does return a fully canonicalized path.
> 
> Factor out a helper that splits off the root part, and have it
> canonicalize the copied part.
> 
> This change was prompted because t1504-ceiling-dirs.sh caught a breakage
> in GIT_CEILING_DIRECTORIES handling on Windows.
> 
> Signed-off-by: Johannes Sixt <j6t@kdbg.org>
> ---
>  This introduces the second #ifdef GIT_WINDOWS_NATIVE in this file.
>  It could be avoided if convert_slashes were defined as a do-nothing
>  on POSIX, but that would not help the other occurrence. Therefore,
>  I suggest to leave it at this.
> 
>  abspath.c | 29 +++++++++++++++++------------
>  1 file changed, 17 insertions(+), 12 deletions(-)
> 
> diff --git a/abspath.c b/abspath.c
> index 79ee310867..1d56f5ed9f 100644
> --- a/abspath.c
> +++ b/abspath.c
> @@ -48,6 +48,19 @@ static void get_next_component(struct strbuf *next, struct strbuf *remaining)
>  	strbuf_remove(remaining, 0, end - remaining->buf);
>  }
>  
> +/* copies root part from remaining to resolved, canonicalizing it on the way */
> +static void get_root_part(struct strbuf *resolved, struct strbuf *remaining)
> +{
> +	int offset = offset_1st_component(remaining->buf);
> +
> +	strbuf_reset(resolved);
> +	strbuf_add(resolved, remaining->buf, offset);
> +#ifdef GIT_WINDOWS_NATIVE
> +	convert_slashes(resolved->buf);
> +#endif