Re: [PATCH v3 07/12] dir: add commentary explaining match_pathspec_item's return value

> The way match_pathspec_item() handles names and pathspecs with trailing
> slash characters, in conjunction with special options like
> DO_MATCH_DIRECTORY and DO_MATCH_LEADING_PATHSPEC were non-obvious, and
> broken until this patch series.  Add a table in a comment explaining the
> intent of how these work.

>
> Signed-off-by: Elijah Newren <newren@gmail.com>
> ---
>  dir.c | 27 +++++++++++++++++++--------
>  1 file changed, 19 insertions(+), 8 deletions(-)
>
> diff --git a/dir.c b/dir.c
> index 47c0a99cb5..3b2fe1701c 100644
> --- a/dir.c
> +++ b/dir.c
> @@ -276,16 +276,27 @@ static int do_read_blob(const struct object_id *oid, struct oid_stat *oid_stat,
>  #define DO_MATCH_LEADING_PATHSPEC (1<<2)
>  
>  /*
> - * Does 'match' match the given name?
> - * A match is found if
> + * Does the given pathspec match the given name?  A match is found if
>   *
> - * (1) the 'match' string is leading directory of 'name', or
> - * (2) the 'match' string is a wildcard and matches 'name', or
> - * (3) the 'match' string is exactly the same as 'name'.
> + * (1) the pathspec string is leading directory of 'name' ("RECURSIVELY"), or
> + * (2) the pathspec string has a leading part matching 'name' ("LEADING"), or
> + * (3) the pathspec string is a wildcard and matches 'name' ("WILDCARD"), or
> + * (4) the pathspec string is exactly the same as 'name' ("EXACT").
>   *
> - * and the return value tells which case it was.
> + * Return value tells which case it was (1-4), or 0 when there is no match.
>   *
> - * It returns 0 when there is no match.
> + * It may be instructive to look at a small table of concrete examples
> + * to understand the differences between 1, 2, and 4:
> + *
> + *                              Pathspecs
> + *                |    a/b    |   a/b/    |   a/b/c
> + *          ------+-----------+-----------+------------
> + *          a/b   |  EXACT    |  EXACT[1] | LEADING[2]
> + *  Names   a/b/  | RECURSIVE |   EXACT   | LEADING[2]
> + *          a/b/c | RECURSIVE | RECURSIVE |   EXACT
> + *
> + * [1] Only if DO_MATCH_DIRECTORY is passed; otherwise, this is NOT a match.
> + * [2] Only if DO_MATCH_LEADING_PATHSPEC is passed; otherwise, not a match.
>   */
>  static int match_pathspec_item(const struct index_state *istate,
>  			       const struct pathspec_item *item, int prefix,
> @@ -353,7 +364,7 @@ static int match_pathspec_item(const struct index_state *istate,
>  			 item->nowildcard_len - prefix))
>  		return MATCHED_FNMATCH;
>  
> -	/* Perform checks to see if "name" is a super set of the pathspec */
> +	/* Perform checks to see if "name" is a leading string of the pathspec */
>  	if (flags & DO_MATCH_LEADING_PATHSPEC) {
>  		/* name is a literal prefix of the pathspec */
>  		int offset = name[namelen-1] == '/' ? 1 : 0;