pack: move approximate object count to object store

The approximate_object_count() function maintains a rough count of
objects in a repository to estimate how long object name abbreviates
should be.  Object names are scoped to a repository and the
appropriate length may differ by repository, so the object count
should not be global.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

object-store.h

@@ -99,6 +99,14 @@ struct raw_object_store {
 	/* A most-recently-used ordered version of the packed_git list. */
 	struct list_head packed_git_mru;
 
+	/*
+	 * A fast, rough count of the number of objects in the repository.
+	 * These two fields are not meant for direct access. Use
+	 * approximate_object_count() instead.
+	 */
+	unsigned long approximate_object_count;
+	unsigned approximate_object_count_valid : 1;
+
 	/*
 	 * Whether packed_git has already been populated with this repository's
 	 * packs.

packfile.c

@@ -803,8 +803,6 @@ static void prepare_packed_git_one(char *objdir, int local)
 	strbuf_release(&path);
 }
 
-static int approximate_object_count_valid;
-
 /*
  * Give a fast, rough count of the number of objects in the repository. This
  * ignores loose objects completely. If you have a lot of them, then either
@@ -814,8 +812,8 @@ static int approximate_object_count_valid;
  */
 unsigned long approximate_object_count(void)
 {
-	static unsigned long count;
-	if (!approximate_object_count_valid) {
+	if (!the_repository->objects->approximate_object_count_valid) {
+		unsigned long count;
 		struct packed_git *p;
 
 		prepare_packed_git();
@@ -825,8 +823,9 @@ unsigned long approximate_object_count(void)
 				continue;
 			count += p->num_objects;
 		}
+		the_repository->objects->approximate_object_count = count;
 	}
-	return count;
+	return the_repository->objects->approximate_object_count;
 }
 
 static void *get_next_packed_git(const void *p)
@@ -901,7 +900,7 @@ void prepare_packed_git(void)
 
 void reprepare_packed_git(void)
 {
-	approximate_object_count_valid = 0;
+	the_repository->objects->approximate_object_count_valid = 0;
 	the_repository->objects->packed_git_initialized = 0;
 	prepare_packed_git();
 }