refactor handling of "other" files in ls-files and status

When the "git status" display code was originally converted
to C, we copied the code from ls-files to discover whether a
pathname returned by read_directory was an "other", or
untracked, file.

Much later, 5698454 updated the code in ls-files to handle
some new cases caused by gitlinks.  This left the code in
wt-status.c broken: it would display submodule directories
as untracked directories. Nobody noticed until now, however,
because unless status.showUntrackedFiles was set to "all",
submodule directories were not actually reported by
read_directory. So the bug was only triggered in the
presence of a submodule _and_ this config option.

This patch pulls the ls-files code into a new function,
cache_name_is_other, and uses it in both places. This should
leave the ls-files functionality the same and fix the bug
in status.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-ls-files.c

@@ -91,39 +91,10 @@ static void show_other_files(struct dir_struct *dir)
 {
 	int i;
 
-
-	/*
-	 * Skip matching and unmerged entries for the paths,
-	 * since we want just "others".
-	 *
-	 * (Matching entries are normally pruned during
-	 * the directory tree walk, but will show up for
-	 * gitlinks because we don't necessarily have
-	 * dir->show_other_directories set to suppress
-	 * them).
-	 */
 	for (i = 0; i < dir->nr; i++) {
 		struct dir_entry *ent = dir->entries[i];
-		int len, pos;
-		struct cache_entry *ce;
-
-		/*
-		 * Remove the '/' at the end that directory
-		 * walking adds for directory entries.
-		 */
-		len = ent->len;
-		if (len && ent->name[len-1] == '/')
-			len--;
-		pos = cache_name_pos(ent->name, len);
-		if (0 <= pos)
-			continue;	/* exact match */
-		pos = -pos - 1;
-		if (pos < active_nr) {
-			ce = active_cache[pos];
-			if (ce_namelen(ce) == len &&
-			    !memcmp(ce->name, ent->name, len))
-				continue; /* Yup, this one exists unmerged */
-		}
+		if (!cache_name_is_other(ent->name, ent->len))
+			continue;
 		show_dir_entry(tag_other, ent);
 	}
 }

cache.h

@@ -270,6 +270,7 @@ static inline void remove_name_hash(struct cache_entry *ce)
 #define ce_match_stat(ce, st, options) ie_match_stat(&the_index, (ce), (st), (options))
 #define ce_modified(ce, st, options) ie_modified(&the_index, (ce), (st), (options))
 #define cache_name_exists(name, namelen, igncase) index_name_exists(&the_index, (name), (namelen), (igncase))
+#define cache_name_is_other(name, namelen) index_name_is_other(&the_index, (name), (namelen))
 #endif
 
 enum object_type {
@@ -382,6 +383,7 @@ extern int add_to_index(struct index_state *, const char *path, struct stat *, i
 extern int add_file_to_index(struct index_state *, const char *path, int flags);
 extern struct cache_entry *make_cache_entry(unsigned int mode, const unsigned char *sha1, const char *path, int stage, int refresh);
 extern int ce_same_name(struct cache_entry *a, struct cache_entry *b);
+extern int index_name_is_other(const struct index_state *, const char *, int);
 
 /* do stat comparison even if CE_VALID is true */
 #define CE_MATCH_IGNORE_VALID		01

read-cache.c

@@ -1480,3 +1480,31 @@ int read_index_unmerged(struct index_state *istate)
 	istate->cache_nr = dst - istate->cache;
 	return !!last;
 }
+
+/*
+ * Returns 1 if the path is an "other" path with respect to
+ * the index; that is, the path is not mentioned in the index at all,
+ * either as a file, a directory with some files in the index,
+ * or as an unmerged entry.
+ *
+ * We helpfully remove a trailing "/" from directories so that
+ * the output of read_directory can be used as-is.
+ */
+int index_name_is_other(const struct index_state *istate, const char *name,
+		int namelen)
+{
+	int pos;
+	if (namelen && name[namelen - 1] == '/')
+		namelen--;
+	pos = index_name_pos(istate, name, namelen);
+	if (0 <= pos)
+		return 0;	/* exact match */
+	pos = -pos - 1;
+	if (pos < istate->cache_nr) {
+		struct cache_entry *ce = istate->cache[pos];
+		if (ce_namelen(ce) == namelen &&
+		    !memcmp(ce->name, name, namelen))
+			return 0; /* Yup, this one exists unmerged */
+	}
+	return 1;
+}

t/t7502-status.sh

@@ -285,6 +285,12 @@ test_expect_success 'status submodule summary is disabled by default' '
 	test_cmp expect output
 '
 
+# we expect the same as the previous test
+test_expect_success 'status --untracked-files=all does not show submodule' '
+	git status --untracked-files=all >output &&
+	test_cmp expect output
+'
+
 head=$(cd sm && git rev-parse --short=7 --verify HEAD)
 
 cat >expect <<EOF

wt-status.c

@@ -275,20 +275,9 @@ static void wt_status_print_untracked(struct wt_status *s)
 
 	read_directory(&dir, ".", "", 0, NULL);
 	for(i = 0; i < dir.nr; i++) {
-		/* check for matching entry, which is unmerged; lifted from
-		 * builtin-ls-files:show_other_files */
 		struct dir_entry *ent = dir.entries[i];
-		int pos = cache_name_pos(ent->name, ent->len);
-		struct cache_entry *ce;
-		if (0 <= pos)
-			die("bug in wt_status_print_untracked");
-		pos = -pos - 1;
-		if (pos < active_nr) {
-			ce = active_cache[pos];
-			if (ce_namelen(ce) == ent->len &&
-			    !memcmp(ce->name, ent->name, ent->len))
-				continue;
-		}
+		if (!cache_name_is_other(ent->name, ent->len))
+			continue;
 		if (!shown_header) {
 			s->workdir_untracked = 1;
 			wt_status_print_header(s, "Untracked files",