Re: [PATCH 3/3] implement pattern matching in ce_path_match

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

Clemens Buchacher <drizzd@aon.at> writes:

> With this patch ce_path_match uses match_pathspec in order to perform
> pattern matching.

We have two conflicting definitions of pattern matching in our system.
I'd make it more explicit which kind of pattern matching you are talking
about here.

The family of operations based on the diff-tree machinery (e.g. path
limited revision walking "git log A..B -- dir1/dir2") define the pattern
matching as "leading path match (exact match is just a special case of
this)".  Other operations that work on paths in the work tree and the
index (e.g. grep, ls-files) uses "leading path match, but fall back to
globbing".

In the longer term we really should unify them by teaching the former to
fall back to globbing without getting undue performance hit, and this
patch may be a step in the right direction.  There are optimizations that
assume the "leading path" semantics to trim the input early and avoid
opening and descending into a tree object if pathspec patterns cannot
possibly match (see tree-diff.c::tree_entry_interesting() for an example),
and we need to teach them to notice a glob wildcard in an earlier part of
a pathspec and to descend into some trees that they would have skipped
with the old definition of pathspec.

> @@ -49,7 +60,7 @@ static void cmd_log_init(int argc, const char **argv, const char *prefix,
>  		rev->always_show_header = 0;
>  	if (DIFF_OPT_TST(&rev->diffopt, FOLLOW_RENAMES)) {
>  		rev->always_show_header = 0;
> -		if (rev->diffopt.nr_paths != 1)
> +		if (rev->diffopt.nr_paths != 1 || has_special(rev->diffopt.paths[0]))
>  			usage("git logs can only follow renames on one pathname at a time");
>  	}

The reason match_pathspec() first tries exact match and then falls back to
globbing is so that the user can say "I have a file whose name ends with a
question mark, please match it literally."  This patch defeats it, but it
probably is a minor point.

1/3 and 2/3 in the series looked good.

Thanks.