add.c: extract new die_if_path_beyond_symlink() for reuse

This will be reused by a new git check-ignore command.

Also document validate_pathspec().

Signed-off-by: Adam Spiers <git@adamspiers.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/add.c

@@ -153,17 +153,19 @@ static void refresh(int verbose, const char **pathspec)
         free(seen);
 }
 
+/*
+ * Normalizes argv relative to prefix, via get_pathspec(), and then
+ * runs die_if_path_beyond_symlink() on each path in the normalized
+ * list.
+ */
 static const char **validate_pathspec(const char **argv, const char *prefix)
 {
 	const char **pathspec = get_pathspec(prefix, argv);
 
 	if (pathspec) {
 		const char **p;
 		for (p = pathspec; *p; p++) {
-			if (has_symlink_leading_path(*p, strlen(*p))) {
-				int len = prefix ? strlen(prefix) : 0;
-				die(_("'%s' is beyond a symbolic link"), *p + len);
-			}
+			die_if_path_beyond_symlink(*p, prefix);
 		}
 	}
 

pathspec.c

@@ -87,3 +87,15 @@ const char *check_path_for_gitlink(const char *path)
 	}
 	return path;
 }
+
+/*
+ * Dies if the given path refers to a file inside a symlinked
+ * directory in the index.
+ */
+void die_if_path_beyond_symlink(const char *path, const char *prefix)
+{
+	if (has_symlink_leading_path(path, strlen(path))) {
+		int len = prefix ? strlen(prefix) : 0;
+		die(_("'%s' is beyond a symbolic link"), path + len);
+	}
+}

pathspec.h

@@ -4,5 +4,6 @@
 extern char *find_pathspecs_matching_against_index(const char **pathspec);
 extern void add_pathspec_matches_against_index(const char **pathspec, char *seen, int specs);
 extern const char *check_path_for_gitlink(const char *path);
+extern void die_if_path_beyond_symlink(const char *path, const char *prefix);
 
 #endif /* PATHSPEC_H */