diff --git a/pathspec.c b/pathspec.c
index ab70fcbe61..f6fbb643ff 100644
--- a/pathspec.c
+++ b/pathspec.c
@@ -525,24 +525,29 @@ static int pathspec_item_cmp(const void *a_, const void *b_)
 	return strcmp(a->match, b->match);
 }
 
-static void NORETURN unsupported_magic(const char *pattern,
-				       unsigned magic)
+void pathspec_magic_names(unsigned magic, struct strbuf *out)
 {
-	struct strbuf sb = STRBUF_INIT;
 	int i;
 	for (i = 0; i < ARRAY_SIZE(pathspec_magic); i++) {
 		const struct pathspec_magic *m = pathspec_magic + i;
 		if (!(magic & m->bit))
 			continue;
-		if (sb.len)
-			strbuf_addstr(&sb, ", ");
+		if (out->len)
+			strbuf_addstr(out, ", ");
 
 		if (m->mnemonic)
-			strbuf_addf(&sb, _("'%s' (mnemonic: '%c')"),
+			strbuf_addf(out, _("'%s' (mnemonic: '%c')"),
 				    m->name, m->mnemonic);
 		else
-			strbuf_addf(&sb, "'%s'", m->name);
+			strbuf_addf(out, "'%s'", m->name);
 	}
+}
+
+static void NORETURN unsupported_magic(const char *pattern,
+				       unsigned magic)
+{
+	struct strbuf sb = STRBUF_INIT;
+	pathspec_magic_names(magic, &sb);
 	/*
 	 * We may want to substitute "this command" with a command
 	 * name. E.g. when "git add -p" or "git add -i" dies when running
diff --git a/pathspec.h b/pathspec.h
index 41f6adfbb4..688aedc553 100644
--- a/pathspec.h
+++ b/pathspec.h
@@ -130,6 +130,14 @@ void parse_pathspec_file(struct pathspec *pathspec,
 void copy_pathspec(struct pathspec *dst, const struct pathspec *src);
 void clear_pathspec(struct pathspec *);
 
+/*
+ * Add a human-readable string to "out" representing the PATHSPEC_* flags set
+ * in "magic". The result is suitable for error messages, but not for
+ * parsing as pathspec magic itself (you get 'icase' with quotes, not
+ * :(icase)).
+ */
+void pathspec_magic_names(unsigned magic, struct strbuf *out);
+
 static inline int ps_strncmp(const struct pathspec_item *item,
 			     const char *s1, const char *s2, size_t n)
 {