Simplify cache API

Earlier, add_file_to_index() invalidated the path in the cache-tree
but remove_file_from_cache() did not, and the user of the latter
needed to invalidate the entry himself.  This led to a few bugs due to
missed invalidate calls already.  This patch makes the management of
cache-tree less error prone by making more invalidate calls from lower
level cache API functions.

The rules are:

 - If you are going to write the index, you should either maintain
   cache_tree correctly.

   - If you cannot, alternatively you can remove the entire cache_tree
     by calling cache_tree_free() before you call write_cache().

   - When you modify the index, cache_tree_invalidate_path() should be
     called with the path you are modifying, to discard the entry from
     the cache-tree structure.

 - The following cache API functions exported from read-cache.c (and
   the macro whose names have "cache" instead of "index")
   automatically call cache_tree_invalidate_path() for you:

   - remove_file_from_index();
   - add_file_to_index();
   - add_index_entry();

   You can modify the index bypassing the above API functions
   (e.g. find an existing cache entry from the index and modify it in
   place).  You need to call cache_tree_invalidate_path() yourself in
   such a case.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-add.c

@@ -103,7 +103,6 @@ static void update_callback(struct diff_queue_struct *q,
 			break;
 		case DIFF_STATUS_DELETED:
 			remove_file_from_cache(path);
-			cache_tree_invalidate_path(active_cache_tree, path);
 			if (verbose)
 				printf("remove '%s'\n", path);
 			break;

builtin-apply.c

@@ -2394,7 +2394,6 @@ static void remove_file(struct patch *patch, int rmdir_empty)
 	if (update_index) {
 		if (remove_file_from_cache(patch->old_name) < 0)
 			die("unable to remove %s from index", patch->old_name);
-		cache_tree_invalidate_path(active_cache_tree, patch->old_name);
 	}
 	if (!cached) {
 		if (S_ISGITLINK(patch->old_mode)) {
@@ -2549,7 +2548,6 @@ static void create_file(struct patch *patch)
 		mode = S_IFREG | 0644;
 	create_one_file(path, mode, buf, size);
 	add_index_file(path, mode, buf, size);
-	cache_tree_invalidate_path(active_cache_tree, path);
 }
 
 /* phase zero is to remove, phase one is to create */

builtin-mv.c

@@ -276,11 +276,8 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 			add_file_to_cache(path, verbose);
 		}
 
-		for (i = 0; i < deleted.nr; i++) {
+		for (i = 0; i < deleted.nr; i++)
-			const char *path = deleted.items[i].path;
+			remove_file_from_cache(deleted.items[i].path);
-			remove_file_from_cache(path);
-			cache_tree_invalidate_path(active_cache_tree, path);
-		}
 
 		if (active_cache_changed) {
 			if (write_cache(newfd, active_cache, active_nr) ||

builtin-rm.c

@@ -227,7 +227,6 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
 
 		if (remove_file_from_cache(path))
 			die("git-rm: unable to remove %s", path);
-		cache_tree_invalidate_path(active_cache_tree, path);
 	}
 
 	if (show_only)

builtin-update-index.c

@@ -195,11 +195,6 @@ static int process_path(const char *path)
 	int len;
 	struct stat st;
 
-	/* We probably want to do this in remove_file_from_cache() and
-	 * add_cache_entry() instead...
-	 */
-	cache_tree_invalidate_path(active_cache_tree, path);
-
 	/*
 	 * First things first: get the stat information, to decide
 	 * what to do about the pathname!
@@ -239,7 +234,6 @@ static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
 		return error("%s: cannot add to the index - missing --add option?",
 			     path);
 	report("add '%s'", path);
-	cache_tree_invalidate_path(active_cache_tree, path);
 	return 0;
 }
 
@@ -284,7 +278,6 @@ static void update_one(const char *path, const char *prefix, int prefix_length)
 			die("Unable to mark file %s", path);
 		goto free_return;
 	}
-	cache_tree_invalidate_path(active_cache_tree, path);
 
 	if (force_remove) {
 		if (remove_file_from_cache(p))
@@ -367,7 +360,6 @@ static void read_index_info(int line_termination)
 				free(path_name);
 			continue;
 		}
-		cache_tree_invalidate_path(active_cache_tree, path_name);
 
 		if (!mode) {
 			/* mode == 0 means there is no such path -- remove */
@@ -474,7 +466,6 @@ static int unresolve_one(const char *path)
 		goto free_return;
 	}
 
-	cache_tree_invalidate_path(active_cache_tree, path);
 	remove_file_from_cache(path);
 	if (add_cache_entry(ce_2, ADD_CACHE_OK_TO_ADD)) {
 		error("%s: cannot add our version to the index.", path);

read-cache.c

@@ -346,6 +346,7 @@ int remove_file_from_index(struct index_state *istate, const char *path)
 	int pos = index_name_pos(istate, path, strlen(path));
 	if (pos < 0)
 		pos = -pos-1;
+	cache_tree_invalidate_path(istate->cache_tree, path);
 	while (pos < istate->cache_nr && !strcmp(istate->cache[pos]->name, path))
 		remove_index_entry_at(istate, pos);
 	return 0;
@@ -430,7 +431,6 @@ int add_file_to_index(struct index_state *istate, const char *path, int verbose)
 		die("unable to add %s to index",path);
 	if (verbose)
 		printf("add '%s'\n", path);
-	cache_tree_invalidate_path(istate->cache_tree, path);
 	return 0;
 }
 
@@ -673,6 +673,7 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
 	int ok_to_replace = option & ADD_CACHE_OK_TO_REPLACE;
 	int skip_df_check = option & ADD_CACHE_SKIP_DFCHECK;
 
+	cache_tree_invalidate_path(istate->cache_tree, ce->name);
 	pos = index_name_pos(istate, ce->name, ntohs(ce->ce_flags));
 
 	/* existing match? Just replace it. */