Re: [PATCH 7/8] longest_ancestor_length(): resolve symlinks before comparing paths

> longest_ancestor_length() relies on a textual comparison of directory
> parts to find the part of path that overlaps with one of the paths in
> prefix_list.  But this doesn't work if any of the prefixes involves a
> symbolic link, because the directories will look different even though
> they might logically refer to the same directory.  So canonicalize the
> paths listed in prefix_list using real_path_if_valid() before trying
> to find matches.
>
> path is already in canonical form, so doesn't need to be canonicalized
> again.
>
> This fixes some problems with using GIT_CEILING_DIRECTORIES that
> contains paths involving symlinks, including t4035 if run with --root
> set to a path involving symlinks.
>
> Remove a number of tests of longest_ancestor_length().  It is awkward
> to test longest_ancestor_length() now, because its new path
> normalization behavior depends on the contents of the whole
> filesystem.  But we can live without the tests, because
> longest_ancestor_length() is now built of reusable components that are
> themselves tested separately: string_list_split(),
> string_list_longest_prefix(), and real_path_if_valid().

> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
> ---
>  path.c                | 17 ++++++++------
>  t/t0060-path-utils.sh | 64 ---------------------------------------------------
>  2 files changed, 10 insertions(+), 71 deletions(-)
>
> diff --git a/path.c b/path.c
> index 5cace83..981bb06 100644
> --- a/path.c
> +++ b/path.c
> @@ -570,22 +570,25 @@ int normalize_path_copy(char *dst, const char *src)
>  
>  static int normalize_path_callback(struct string_list_item *item, void *cb_data)
>  {
> -	char buf[PATH_MAX+2];
> +	char *buf;
>  	const char *ceil = item->string;
> -	int len = strlen(ceil);
> +	const char *realpath;
> +	int len;
>  
> -	if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
> +	if (!*ceil || !is_absolute_path(ceil))
>  		return 0;
> -	memcpy(buf, ceil, len+1);
> -	if (normalize_path_copy(buf, buf) < 0)
> +	realpath = real_path_if_valid(ceil);
> +	if (!realpath)
>  		return 0;
> -	len = strlen(buf);
> +	len = strlen(realpath);
> +	buf = xmalloc(len + 2); /* Leave space for possible trailing slash */
> +	strcpy(buf, realpath);
>  	if (len == 0 || buf[len-1] != '/') {
>  		buf[len++] = '/';
>  		buf[len++] = '\0';
>  	}