entry: factor out unlink_entry function

Factor out the 'unlink_entry()' function from unpack-trees.c to
entry.c.  It will be used in other places as well in subsequent
steps.

As it's no longer a static function, also move the documentation to
the header file to make it more discoverable.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -1542,6 +1542,11 @@ struct checkout {
 extern int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *topath);
 extern void enable_delayed_checkout(struct checkout *state);
 extern int finish_delayed_checkout(struct checkout *state);
+/*
+ * Unlink the last component and schedule the leading directories for
+ * removal, such that empty directories get removed.
+ */
+extern void unlink_entry(const struct cache_entry *ce);
 
 struct cache_def {
 	struct strbuf path;

entry.c

@@ -508,3 +508,18 @@ int checkout_entry(struct cache_entry *ce,
 	create_directories(path.buf, path.len, state);
 	return write_entry(ce, path.buf, state, 0);
 }
+
+void unlink_entry(const struct cache_entry *ce)
+{
+	const struct submodule *sub = submodule_from_ce(ce);
+	if (sub) {
+		/* state.force is set at the caller. */
+		submodule_move_head(ce->name, "HEAD", NULL,
+				    SUBMODULE_MOVE_HEAD_FORCE);
+	}
+	if (!check_leading_path(ce->name, ce_namelen(ce)))
+		return;
+	if (remove_or_warn(ce->ce_mode, ce->name))
+		return;
+	schedule_dir_for_removal(ce->name, ce_namelen(ce));
+}

unpack-trees.c

@@ -300,25 +300,6 @@ static void load_gitmodules_file(struct index_state *index,
 	}
 }
 
-/*
- * Unlink the last component and schedule the leading directories for
- * removal, such that empty directories get removed.
- */
-static void unlink_entry(const struct cache_entry *ce)
-{
-	const struct submodule *sub = submodule_from_ce(ce);
-	if (sub) {
-		/* state.force is set at the caller. */
-		submodule_move_head(ce->name, "HEAD", NULL,
-				    SUBMODULE_MOVE_HEAD_FORCE);
-	}
-	if (!check_leading_path(ce->name, ce_namelen(ce)))
-		return;
-	if (remove_or_warn(ce->ce_mode, ce->name))
-		return;
-	schedule_dir_for_removal(ce->name, ce_namelen(ce));
-}
-
 static struct progress *get_progress(struct unpack_trees_options *o)
 {
 	unsigned cnt = 0, total = 0;