Re: [PATCH 11/18] mingw: support renaming symlinks

> From: Karsten Blees <blees@dcon.de>
> 
> Older MSVCRT's `_wrename()` function cannot rename symlinks over
> existing files: it returns success without doing anything. Newer
> MSVCR*.dll versions probably do not share this problem: according to CRT
> sources, they just call `MoveFileEx()` with the `MOVEFILE_COPY_ALLOWED`
> flag.
> 
> Avoid the `_wrename()` call, and go with directly calling
> `MoveFileEx()`, with proper error handling of course.
> 
> Signed-off-by: Karsten Blees <blees@dcon.de>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>  compat/mingw.c | 38 ++++++++++++++++----------------------
>  1 file changed, 16 insertions(+), 22 deletions(-)
> 
> diff --git a/compat/mingw.c b/compat/mingw.c
> index b1cc30d0f1..55f0bb478e 100644
> --- a/compat/mingw.c
> +++ b/compat/mingw.c
> @@ -2275,7 +2275,7 @@ int mingw_accept(int sockfd1, struct sockaddr *sa, socklen_t *sz)
>  int mingw_rename(const char *pold, const char *pnew)
>  {
>  	static int supports_file_rename_info_ex = 1;
> -	DWORD attrs, gle;
> +	DWORD attrs = INVALID_FILE_ATTRIBUTES, gle;
>  	int tries = 0;
>  	wchar_t wpold[MAX_PATH], wpnew[MAX_PATH];
>  	int wpnew_len;
> @@ -2286,15 +2286,6 @@ int mingw_rename(const char *pold, const char *pnew)
>  	if (wpnew_len < 0)
>  		return -1;
>  
> -	/*
> -	 * Try native rename() first to get errno right.
> -	 * It is based on MoveFile(), which cannot overwrite existing files.
> -	 */
> -	if (!_wrename(wpold, wpnew))
> -		return 0;
> -	if (errno != EEXIST)
> -		return -1;
> -
>  repeat:
>  	if (supports_file_rename_info_ex) {
>  		/*
> @@ -2370,13 +2361,22 @@ repeat:
>  		 * to retry.
>  		 */
>  	} else {
> -		if (MoveFileExW(wpold, wpnew, MOVEFILE_REPLACE_EXISTING))
> +		if (MoveFileExW(wpold, wpnew,
> +				MOVEFILE_REPLACE_EXISTING | MOVEFILE_COPY_ALLOWED))
>  			return 0;
>  		gle = GetLastError();
>  	}
>  
> -	/* TODO: translate more errors */
> -	if (gle == ERROR_ACCESS_DENIED &&
> +	/* revert file attributes on failure */
> +	if (attrs != INVALID_FILE_ATTRIBUTES)
> +		SetFileAttributesW(wpnew, attrs);
> +
> +	if (!is_file_in_use_error(gle)) {
> +		errno = err_win_to_posix(gle);
> +		return -1;
> +	}
> +
> +	if (attrs == INVALID_FILE_ATTRIBUTES &&
>  	    (attrs = GetFileAttributesW(wpnew)) != INVALID_FILE_ATTRIBUTES) {
>  		if (attrs & FILE_ATTRIBUTE_DIRECTORY) {
>  			DWORD attrsold = GetFileAttributesW(wpold);
> @@ -2388,16 +2388,10 @@ repeat:
>  			return -1;
>  		}
>  		if ((attrs & FILE_ATTRIBUTE_READONLY) &&
> -		    SetFileAttributesW(wpnew, attrs & ~FILE_ATTRIBUTE_READONLY)) {
> -			if (MoveFileExW(wpold, wpnew, MOVEFILE_REPLACE_EXISTING))
> -				return 0;
> -			gle = GetLastError();
> -			/* revert file attributes on failure */
> -			SetFileAttributesW(wpnew, attrs);
> -		}
> +		    SetFileAttributesW(wpnew, attrs & ~FILE_ATTRIBUTE_READONLY))
> +			goto repeat;
>  	}
> -	if (gle == ERROR_ACCESS_DENIED &&
> -	       retry_ask_yes_no(&tries, "Rename from '%s' to '%s' failed. "
> +	if (retry_ask_yes_no(&tries, "Rename from '%s' to '%s' failed. "
>  		       "Should I try again?", pold, pnew))
>  		goto repeat;
>