dir.c: support marking some patterns already matched

Given path "a" and the pattern "a", it's matched. But if we throw path
"a/b" to pattern "a", the code fails to realize that if "a" matches
"a" then "a/b" should also be matched.

When the pattern is matched the first time, we can mark it "sticky", so
that all files and dirs inside the matched path also matches. This is a
simpler solution than modify all match scenarios to fix that.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

dir.c

@@ -521,6 +521,7 @@ void add_exclude(const char *string, const char *base,
 	x->baselen = baselen;
 	x->flags = flags;
 	x->srcpos = srcpos;
+	string_list_init(&x->sticky_paths, 1);
 	ALLOC_GROW(el->excludes, el->nr + 1, el->alloc);
 	el->excludes[el->nr++] = x;
 	x->el = el;
@@ -561,8 +562,10 @@ void clear_exclude_list(struct exclude_list *el)
 {
 	int i;
 
-	for (i = 0; i < el->nr; i++)
+	for (i = 0; i < el->nr; i++) {
+		string_list_clear(&el->excludes[i]->sticky_paths, 0);
 		free(el->excludes[i]);
+	}
 	free(el->excludes);
 	free(el->filebuf);
 
@@ -889,6 +892,44 @@ int match_pathname(const char *pathname, int pathlen,
 				 WM_PATHNAME) == 0;
 }
 
+static void add_sticky(struct exclude *exc, const char *pathname, int pathlen)
+{
+	struct strbuf sb = STRBUF_INIT;
+	int i;
+
+	for (i = exc->sticky_paths.nr - 1; i >= 0; i--) {
+		const char *sticky = exc->sticky_paths.items[i].string;
+		int len = strlen(sticky);
+
+		if (pathlen < len && sticky[pathlen] == '/' &&
+		    !strncmp(pathname, sticky, pathlen))
+			return;
+	}
+
+	strbuf_add(&sb, pathname, pathlen);
+	string_list_append_nodup(&exc->sticky_paths, strbuf_detach(&sb, NULL));
+}
+
+static int match_sticky(struct exclude *exc, const char *pathname, int pathlen, int dtype)
+{
+	int i;
+
+	for (i = exc->sticky_paths.nr - 1; i >= 0; i--) {
+		const char *sticky = exc->sticky_paths.items[i].string;
+		int len = strlen(sticky);
+
+		if (pathlen == len && dtype == DT_DIR &&
+		    !strncmp(pathname, sticky, len))
+			return 1;
+
+		if (pathlen > len && pathname[len] == '/' &&
+		    !strncmp(pathname, sticky, len))
+			return 1;
+	}
+
+	return 0;
+}
+
 /*
  * Scan the given exclude list in reverse to see whether pathname
  * should be ignored.  The first match (i.e. the last on the list), if
@@ -914,6 +955,16 @@ static struct exclude *last_exclude_matching_from_list(const char *pathname,
 		const char *exclude = x->pattern;
 		int prefix = x->nowildcardlen;
 
+		if (x->sticky_paths.nr) {
+			if (*dtype == DT_UNKNOWN)
+				*dtype = get_dtype(NULL, pathname, pathlen);
+			if (match_sticky(x, pathname, pathlen, *dtype)) {
+				exc = x;
+				break;
+			}
+			continue;
+		}
+
 		if (x->flags & EXC_FLAG_MUSTBEDIR) {
 			if (*dtype == DT_UNKNOWN)
 				*dtype = get_dtype(NULL, pathname, pathlen);
@@ -947,9 +998,10 @@ static struct exclude *last_exclude_matching_from_list(const char *pathname,
 		return NULL;
 	}
 
-	trace_printf_key(&trace_exclude, "exclude: %.*s vs %s at line %d => %s\n",
+	trace_printf_key(&trace_exclude, "exclude: %.*s vs %s at line %d => %s%s\n",
 			 pathlen, pathname, exc->pattern, exc->srcpos,
-			 exc->flags & EXC_FLAG_NEGATIVE ? "no" : "yes");
+			 exc->flags & EXC_FLAG_NEGATIVE ? "no" : "yes",
+			 exc->sticky_paths.nr ? " (stuck)" : "");
 	return exc;
 }
 
@@ -2005,6 +2057,25 @@ static struct untracked_cache_dir *validate_untracked_cache(struct dir_struct *d
 	return root;
 }
 
+static void clear_sticky(struct dir_struct *dir)
+{
+	struct exclude_list_group *g;
+	struct exclude_list *el;
+	struct exclude *x;
+	int i, j, k;
+
+	for (i = EXC_CMDL; i <= EXC_FILE; i++) {
+		g = &dir->exclude_list_group[i];
+		for (j = g->nr - 1; j >= 0; j--) {
+			el = &g->el[j];
+			for (k = el->nr - 1; 0 <= k; k--) {
+				x = el->excludes[k];
+				string_list_clear(&x->sticky_paths, 0);
+			}
+		}
+	}
+}
+
 int read_directory(struct dir_struct *dir, const char *path, int len, const struct pathspec *pathspec)
 {
 	struct path_simplify *simplify;

dir.h

@@ -4,6 +4,7 @@
 /* See Documentation/technical/api-directory-listing.txt */
 
 #include "strbuf.h"
+#include "string-list.h"
 
 struct dir_entry {
 	unsigned int len;
@@ -34,6 +35,8 @@ struct exclude {
 	 * and from -1 decrementing for patterns from CLI args.
 	 */
 	int srcpos;
+
+	struct string_list sticky_paths;
 };
 
 /*