[PATCH 5/5] unpack-trees: rename 'is_excluded_from_list()'

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <dstolee@microsoft.com>

The first consumer of pattern-matching filenames was the
.gitignore feature. In that context, storing a list of patterns
as a 'struct exclude_list'  makes sense. However, the
sparse-checkout feature then adopted these structures and methods,
but with the opposite meaning: these patterns match the files
that should be included!

Now that this library is renamed to use 'struct pattern_list'
and 'struct pattern', we can now rename the method used by
the sparse-checkout feature to determine which paths should
appear in the working directory.

The method is_excluded_from_list() is only used by the
sparse-checkout logic in unpack-trees and list-objects-filter.
The confusing part is that it returned 1 for "excluded" (i.e.
it matches the list of exclusions) but that really manes that
the path matched the list of patterns for _inclusion_ in the
working directory.

Rename the method to be path_matches_pattern_list() and have
it return an explicit 'enum pattern_match_result'. Here, the
values MATCHED = 1, UNMATCHED = 0, and UNDECIDED = -1 agree
with the previous integer values. This shift allows future
consumers to better understand what the retur values mean,
and provides more type checking for handling those values.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 dir.c                 | 25 +++++++++++++++++--------
 dir.h                 | 21 +++++++++++++++++----
 list-objects-filter.c | 29 +++++++++++++++--------------
 unpack-trees.c        | 39 +++++++++++++++++++++++----------------
 4 files changed, 72 insertions(+), 42 deletions(-)

diff --git a/dir.c b/dir.c
index b057bd3d95..34972abdaf 100644
--- a/dir.c
+++ b/dir.c
@@ -1072,19 +1072,28 @@ static struct path_pattern *last_matching_pattern_from_list(const char *pathname
 }
 
 /*
- * Scan the list and let the last match determine the fate.
- * Return 1 for exclude, 0 for include and -1 for undecided.
+ * Scan the list of patterns to determine if the ordered list
+ * of patterns matches on 'pathname'.
+ *
+ * Return 1 for a match, 0 for not matched and -1 for undecided.
  */
-int is_excluded_from_list(const char *pathname,
-			  int pathlen, const char *basename, int *dtype,
-			  struct pattern_list *pl, struct index_state *istate)
+enum pattern_match_result path_matches_pattern_list(
+				const char *pathname, int pathlen,
+				const char *basename, int *dtype,
+				struct pattern_list *pl,
+				struct index_state *istate)
 {
 	struct path_pattern *pattern;
 	pattern = last_matching_pattern_from_list(pathname, pathlen, basename,
 						  dtype, pl, istate);
-	if (pattern)
-		return pattern->flags & PATTERN_FLAG_NEGATIVE ? 0 : 1;
-	return -1; /* undecided */
+	if (pattern) {
+		if (pattern->flags & PATTERN_FLAG_NEGATIVE)
+			return NOT_MATCHED;
+		else
+			return MATCHED;
+	}
+
+	return UNDECIDED;
 }
 
 static struct path_pattern *last_matching_pattern_from_lists(
diff --git a/dir.h b/dir.h
index 7babf31d88..608696c958 100644
--- a/dir.h
+++ b/dir.h
@@ -230,10 +230,23 @@ int read_directory(struct dir_struct *, struct index_state *istate,
 		   const char *path, int len,
 		   const struct pathspec *pathspec);
 
-int is_excluded_from_list(const char *pathname, int pathlen,
-			  const char *basename, int *dtype,
-			  struct pattern_list *pl,
-			  struct index_state *istate);
+enum pattern_match_result {
+	UNDECIDED = -1,
+	NOT_MATCHED = 0,
+	MATCHED = 1,
+};
+
+/*
+ * Scan the list of patterns to determine if the ordered list
+ * of patterns matches on 'pathname'.
+ *
+ * Return 1 for a match, 0 for not matched and -1 for undecided.
+ */
+enum pattern_match_result path_matches_pattern_list(const char *pathname,
+				int pathlen,
+				const char *basename, int *dtype,
+				struct pattern_list *pl,
+				struct index_state *istate);
 struct dir_entry *dir_add_ignored(struct dir_struct *dir,
 				  struct index_state *istate,
 				  const char *pathname, int len);
diff --git a/list-objects-filter.c b/list-objects-filter.c
index ccd58e61c3..d624f1c898 100644
--- a/list-objects-filter.c
+++ b/list-objects-filter.c
@@ -328,12 +328,12 @@ static void filter_blobs_limit__init(
  */
 struct frame {
 	/*
-	 * defval is the usual default include/exclude value that
+	 * default_match is the usual default include/exclude value that
 	 * should be inherited as we recurse into directories based
 	 * upon pattern matching of the directory itself or of a
 	 * containing directory.
 	 */
-	int defval;
+	enum pattern_match_result default_match;
 
 	/*
 	 * 1 if the directory (recursively) contains any provisionally
@@ -363,8 +363,9 @@ static enum list_objects_filter_result filter_sparse(
 	void *filter_data_)
 {
 	struct filter_sparse_data *filter_data = filter_data_;
-	int val, dtype;
+	int dtype;
 	struct frame *frame;
+	enum pattern_match_result match;
 
 	switch (filter_situation) {
 	default:
@@ -373,15 +374,15 @@ static enum list_objects_filter_result filter_sparse(
 	case LOFS_BEGIN_TREE:
 		assert(obj->type == OBJ_TREE);
 		dtype = DT_DIR;
-		val = is_excluded_from_list(pathname, strlen(pathname),
-					    filename, &dtype, &filter_data->pl,
-					    r->index);
-		if (val < 0)
-			val = filter_data->array_frame[filter_data->nr - 1].defval;
+		match = path_matches_pattern_list(pathname, strlen(pathname),
+						  filename, &dtype, &filter_data->pl,
+						  r->index);
+		if (match == UNDECIDED)
+			match = filter_data->array_frame[filter_data->nr - 1].default_match;
 
 		ALLOC_GROW(filter_data->array_frame, filter_data->nr + 1,
 			   filter_data->alloc);
-		filter_data->array_frame[filter_data->nr].defval = val;
+		filter_data->array_frame[filter_data->nr].default_match = match;
 		filter_data->array_frame[filter_data->nr].child_prov_omit = 0;
 		filter_data->nr++;
 
@@ -435,12 +436,12 @@ static enum list_objects_filter_result filter_sparse(
 		frame = &filter_data->array_frame[filter_data->nr - 1];
 
 		dtype = DT_REG;
-		val = is_excluded_from_list(pathname, strlen(pathname),
+		match = path_matches_pattern_list(pathname, strlen(pathname),
 					    filename, &dtype, &filter_data->pl,
 					    r->index);
-		if (val < 0)
-			val = frame->defval;
-		if (val > 0) {
+		if (match == UNDECIDED)
+			match = frame->default_match;
+		if (match == MATCHED) {
 			if (omits)
 				oidset_remove(omits, &obj->oid);
 			return LOFR_MARK_SEEN | LOFR_DO_SHOW;
@@ -487,7 +488,7 @@ static void filter_sparse_oid__init(
 		die("could not load filter specification");
 
 	ALLOC_GROW(d->array_frame, d->nr + 1, d->alloc);
-	d->array_frame[d->nr].defval = 0; /* default to include */
+	d->array_frame[d->nr].default_match = 0; /* default to include */
 	d->array_frame[d->nr].child_prov_omit = 0;
 	d->nr++;
 
diff --git a/unpack-trees.c b/unpack-trees.c
index 902a799aeb..cd548f4fa2 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -1265,7 +1265,8 @@ static int clear_ce_flags_1(struct index_state *istate,
 			    struct cache_entry **cache, int nr,
 			    struct strbuf *prefix,
 			    int select_mask, int clear_mask,
-			    struct pattern_list *pl, int defval);
+			    struct pattern_list *pl,
+			    enum pattern_match_result default_match);
 
 /* Whole directory matching */
 static int clear_ce_flags_dir(struct index_state *istate,
@@ -1273,19 +1274,21 @@ static int clear_ce_flags_dir(struct index_state *istate,
 			      struct strbuf *prefix,
 			      char *basename,
 			      int select_mask, int clear_mask,
-			      struct pattern_list *pl, int defval)
+			      struct pattern_list *pl,
+			      enum pattern_match_result default_match)
 {
 	struct cache_entry **cache_end;
 	int dtype = DT_DIR;
-	int ret = is_excluded_from_list(prefix->buf, prefix->len,
-					basename, &dtype, pl, istate);
 	int rc;
+	enum pattern_match_result ret;
+	ret = path_matches_pattern_list(prefix->buf, prefix->len,
+					basename, &dtype, pl, istate);
 
 	strbuf_addch(prefix, '/');
 
 	/* If undecided, use matching result of parent dir in defval */
-	if (ret < 0)
-		ret = defval;
+	if (ret == UNDECIDED)
+		ret = default_match;
 
 	for (cache_end = cache; cache_end != cache + nr; cache_end++) {
 		struct cache_entry *ce = *cache_end;
@@ -1298,7 +1301,7 @@ static int clear_ce_flags_dir(struct index_state *istate,
 	 * with ret (iow, we know in advance the incl/excl
 	 * decision for the entire directory), clear flag here without
 	 * calling clear_ce_flags_1(). That function will call
-	 * the expensive is_excluded_from_list() on every entry.
+	 * the expensive path_matches_pattern_list() on every entry.
 	 */
 	rc = clear_ce_flags_1(istate, cache, cache_end - cache,
 			      prefix,
@@ -1327,7 +1330,8 @@ static int clear_ce_flags_1(struct index_state *istate,
 			    struct cache_entry **cache, int nr,
 			    struct strbuf *prefix,
 			    int select_mask, int clear_mask,
-			    struct pattern_list *pl, int defval)
+			    struct pattern_list *pl,
+			    enum pattern_match_result default_match)
 {
 	struct cache_entry **cache_end = cache + nr;
 
@@ -1338,7 +1342,8 @@ static int clear_ce_flags_1(struct index_state *istate,
 	while(cache != cache_end) {
 		struct cache_entry *ce = *cache;
 		const char *name, *slash;
-		int len, dtype, ret;
+		int len, dtype;
+		enum pattern_match_result ret;
 
 		if (select_mask && !(ce->ce_flags & select_mask)) {
 			cache++;
@@ -1362,7 +1367,7 @@ static int clear_ce_flags_1(struct index_state *istate,
 						       prefix,
 						       prefix->buf + prefix->len - len,
 						       select_mask, clear_mask,
-						       pl, defval);
+						       pl, default_match);
 
 			/* clear_c_f_dir eats a whole dir already? */
 			if (processed) {
@@ -1374,18 +1379,20 @@ static int clear_ce_flags_1(struct index_state *istate,
 			strbuf_addch(prefix, '/');
 			cache += clear_ce_flags_1(istate, cache, cache_end - cache,
 						  prefix,
-						  select_mask, clear_mask, pl, defval);
+						  select_mask, clear_mask, pl,
+						  default_match);
 			strbuf_setlen(prefix, prefix->len - len - 1);
 			continue;
 		}
 
 		/* Non-directory */
 		dtype = ce_to_dtype(ce);
-		ret = is_excluded_from_list(ce->name, ce_namelen(ce),
-					    name, &dtype, pl, istate);
-		if (ret < 0)
-			ret = defval;
-		if (ret > 0)
+		ret = path_matches_pattern_list(ce->name,
+						ce_namelen(ce),
+						name, &dtype, pl, istate);
+		if (ret == UNDECIDED)
+			ret = default_match;
+		if (ret == MATCHED)
 			ce->ce_flags &= ~clear_mask;
 		cache++;
 	}
-- 
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