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

Junio C Hamano [off-list ref] writes:

Clemens Buchacher [off-list ref] writes:

quoted

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.

Actually there was an earlier attempt that resulted in the pathspec
matching tree traverser builtin-grep uses.  Even though it has to work
with trees (when grepping inside a tree-ish) and has optimizations not to
open unnecessary subtrees similar to the one the diff-tree machinery has,
it also knows how to handle globs.  If we were to pick one of existing
implementations for the longer term unification, I think that is probably
the one we should build on top of.