path: expose do_git_path() as repo_git_pathv()

We're about to move functions of the "path" subsytem that do not use a
`struct repository` into "path.h" as static inlined functions. This will
require us to call `do_git_path()`, which is internal to "path.c".

Expose the function as `repo_git_pathv()` to prepare for the change.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

path.h

@@ -66,6 +66,14 @@ char *repo_git_path(const struct repository *repo,
 		    const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
 
+/*
+ * Print a path into the git directory of repository `repo` into the provided
+ * buffer.
+ */
+void repo_git_pathv(const struct repository *repo,
+		    const struct worktree *wt, struct strbuf *buf,
+		    const char *fmt, va_list args);
+
 /*
  * Construct a path into the git directory of repository `repo` and append it
  * to the provided buffer `sb`.