Merge branch 'nd/split-index'

An experiment to use two files (the base file and incremental
changes relative to it) to represent the index to reduce I/O cost
of rewriting a large index when only small part of the working tree
changes.

* nd/split-index: (32 commits)
  t1700: new tests for split-index mode
  t2104: make sure split index mode is off for the version test
  read-cache: force split index mode with GIT_TEST_SPLIT_INDEX
  read-tree: note about dropping split-index mode or index version
  read-tree: force split-index mode off on --index-output
  rev-parse: add --shared-index-path to get shared index path
  update-index --split-index: do not split if $GIT_DIR is read only
  update-index: new options to enable/disable split index mode
  split-index: strip pathname of on-disk replaced entries
  split-index: do not invalidate cache-tree at read time
  split-index: the reading part
  split-index: the writing part
  read-cache: mark updated entries for split index
  read-cache: save deleted entries in split index
  read-cache: mark new entries for split index
  read-cache: split-index mode
  read-cache: save index SHA-1 after reading
  entry.c: update cache_changed if refresh_cache is set in checkout_entry()
  cache-tree: mark istate->cache_changed on prime_cache_tree()
  cache-tree: mark istate->cache_changed on cache tree update
  ...

1 files changed, 28 insertions, 24 deletions

diff --git a/cache-tree.c b/cache-tree.c
index 7fa524a113..c53f7de2b1 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -98,7 +98,7 @@ struct cache_tree_sub *cache_tree_sub(struct cache_tree *it, const char *path)
 	return find_subtree(it, path, pathlen, 1);
 }
 
-void cache_tree_invalidate_path(struct cache_tree *it, const char *path)
+static int do_invalidate_path(struct cache_tree *it, const char *path)
 {
 	/* a/b/c
 	 * ==> invalidate self
@@ -116,7 +116,7 @@ void cache_tree_invalidate_path(struct cache_tree *it, const char *path)
 #endif
 
 	if (!it)
-		return;
+		return 0;
 	slash = strchrnul(path, '/');
 	namelen = slash - path;
 	it->entry_count = -1;
@@ -137,14 +137,21 @@ void cache_tree_invalidate_path(struct cache_tree *it, const char *path)
 				(it->subtree_nr - pos - 1));
 			it->subtree_nr--;
 		}
-		return;
+		return 1;
 	}
 	down = find_subtree(it, path, namelen, 0);
 	if (down)
-		cache_tree_invalidate_path(down->cache_tree, slash + 1);
+		do_invalidate_path(down->cache_tree, slash + 1);
+	return 1;
 }
 
-static int verify_cache(const struct cache_entry * const *cache,
+void cache_tree_invalidate_path(struct index_state *istate, const char *path)
+{
+	if (do_invalidate_path(istate->cache_tree, path))
+		istate->cache_changed |= CACHE_TREE_CHANGED;
+}
+
+static int verify_cache(struct cache_entry **cache,
 			int entries, int flags)
 {
 	int i, funny;
@@ -229,7 +236,7 @@ int cache_tree_fully_valid(struct cache_tree *it)
 }
 
 static int update_one(struct cache_tree *it,
-		      const struct cache_entry * const *cache,
+		      struct cache_entry **cache,
 		      int entries,
 		      const char *base,
 		      int baselen,
@@ -391,18 +398,19 @@ static int update_one(struct cache_tree *it,
 	return i;
 }
 
-int cache_tree_update(struct cache_tree *it,
-		      const struct cache_entry * const *cache,
-		      int entries,
-		      int flags)
+int cache_tree_update(struct index_state *istate, int flags)
 {
-	int i, skip;
-	i = verify_cache(cache, entries, flags);
+	struct cache_tree *it = istate->cache_tree;
+	struct cache_entry **cache = istate->cache;
+	int entries = istate->cache_nr;
+	int skip, i = verify_cache(cache, entries, flags);
+
 	if (i)
 		return i;
 	i = update_one(it, cache, entries, "", 0, &skip, flags);
 	if (i < 0)
 		return i;
+	istate->cache_changed |= CACHE_TREE_CHANGED;
 	return 0;
 }
 
@@ -590,13 +598,10 @@ int write_cache_as_tree(unsigned char *sha1, int flags, const char *prefix)
 
 	was_valid = cache_tree_fully_valid(active_cache_tree);
 	if (!was_valid) {
-		if (cache_tree_update(active_cache_tree,
-				      (const struct cache_entry * const *)active_cache,
-				      active_nr, flags) < 0)
+		if (cache_tree_update(&the_index, flags) < 0)
 			return WRITE_TREE_UNMERGED_INDEX;
 		if (0 <= newfd) {
-			if (!write_cache(newfd, active_cache, active_nr) &&
-			    !commit_lock_file(lock_file))
+			if (!write_locked_index(&the_index, lock_file, COMMIT_LOCK))
 				newfd = -1;
 		}
 		/* Not being able to write is fine -- we are only interested
@@ -649,11 +654,12 @@ static void prime_cache_tree_rec(struct cache_tree *it, struct tree *tree)
 	it->entry_count = cnt;
 }
 
-void prime_cache_tree(struct cache_tree **it, struct tree *tree)
+void prime_cache_tree(struct index_state *istate, struct tree *tree)
 {
-	cache_tree_free(it);
-	*it = cache_tree();
-	prime_cache_tree_rec(*it, tree);
+	cache_tree_free(&istate->cache_tree);
+	istate->cache_tree = cache_tree();
+	prime_cache_tree_rec(istate->cache_tree, tree);
+	istate->cache_changed |= CACHE_TREE_CHANGED;
 }
 
 /*
@@ -692,7 +698,5 @@ int update_main_cache_tree(int flags)
 {
 	if (!the_index.cache_tree)
 		the_index.cache_tree = cache_tree();
-	return cache_tree_update(the_index.cache_tree,
-				 (const struct cache_entry * const *)the_index.cache,
-				 the_index.cache_nr, flags);
+	return cache_tree_update(&the_index, flags);
 }