dir.c: free "ident" and "exclude_per_dir" in "struct untracked_cache"

When the "ident" member of the structure was added in
1e8fef6 (untracked cache: guard and disable on system changes,
2015-03-08) this function wasn't updated to free it. Let's do so.

Let's also free the "exclude_per_dir" memory we've been leaking
since[1], while making sure not to free() the constant ".gitignore"
string we add by default[2].

As we now have three struct members we're freeing let's change
free_untracked_cache() to return early if "uc" isn't defined. We won't
hand it to free() now, but that was just for convenience, once we're
dealing with >=2 struct members this pattern is more convenient.

1. f9e6c64 (untracked cache: load from UNTR index extension,
   2015-03-08)
2. 039bc64 (core.excludesfile clean-up, 2007-11-14)

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Taylor Blau <[email protected]>

Author: avar

dir.c

@@ -3581,8 +3581,12 @@ static void free_untracked(struct untracked_cache_dir *ucd)
 
 void free_untracked_cache(struct untracked_cache *uc)
 {
-	if (uc)
-		free_untracked(uc->root);
+	if (!uc)
+		return;
+
+	free(uc->exclude_per_dir_to_free);
+	strbuf_release(&uc->ident);
+	free_untracked(uc->root);
 	free(uc);
 }
 
@@ -3739,7 +3743,7 @@ struct untracked_cache *read_untracked_extension(const void *data, unsigned long
 		      next + offset + hashsz);
 	uc->dir_flags = get_be32(next + ouc_offset(dir_flags));
 	exclude_per_dir = (const char *)next + exclude_per_dir_offset;
-	uc->exclude_per_dir = xstrdup(exclude_per_dir);
+	uc->exclude_per_dir = uc->exclude_per_dir_to_free = xstrdup(exclude_per_dir);
 	/* NUL after exclude_per_dir is covered by sizeof(*ouc) */
 	next += exclude_per_dir_offset + strlen(exclude_per_dir) + 1;
 	if (next >= end)

dir.h

@@ -188,6 +188,7 @@ struct untracked_cache {
 	struct oid_stat ss_info_exclude;
 	struct oid_stat ss_excludes_file;
 	const char *exclude_per_dir;
+	char *exclude_per_dir_to_free;
 	struct strbuf ident;
 	/*
 	 * dir_struct#flags must match dir_flags or the untracked