merge-recursive: do not use on-file index when not needed.

This revamps the merge-recursive implementation following the
outline in:

	Message-ID: <7v8xgileza.fsf@assigned-by-dhcp.cox.net>

There is no need to write out the index until the very end just
once from merge-recursive.  Also there is no need to write out
the resulting tree object for the simple case of merging with a
single merge base.

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 46 insertions, 123 deletions

diff --git a/merge-recursive.c b/merge-recursive.c
index aab4c34588..5237021309 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -110,35 +110,6 @@ static void output_commit_title(struct commit *commit)
 	}
 }
 
-static const char *current_index_file = NULL;
-static const char *original_index_file;
-static const char *temporary_index_file;
-static int cache_dirty = 0;
-
-static int flush_cache(void)
-{
-	/* flush temporary index */
-	struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
-	int fd = hold_lock_file_for_update(lock, current_index_file, 1);
-	if (write_cache(fd, active_cache, active_nr) ||
-			close(fd) || commit_lock_file(lock))
-		die ("unable to write %s", current_index_file);
-	discard_cache();
-	cache_dirty = 0;
-	return 0;
-}
-
-static void setup_index(int temp)
-{
-	current_index_file = temp ? temporary_index_file: original_index_file;
-	if (cache_dirty) {
-		discard_cache();
-		cache_dirty = 0;
-	}
-	unlink(temporary_index_file);
-	discard_cache();
-}
-
 static struct cache_entry *make_cache_entry(unsigned int mode,
 		const unsigned char *sha1, const char *path, int stage, int refresh)
 {
@@ -167,9 +138,6 @@ static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
 		const char *path, int stage, int refresh, int options)
 {
 	struct cache_entry *ce;
-	if (!cache_dirty)
-		read_cache_from(current_index_file);
-	cache_dirty++;
 	ce = make_cache_entry(mode, sha1 ? sha1 : null_sha1, path, stage, refresh);
 	if (!ce)
 		return error("cache_addinfo failed: %s", strerror(cache_errno));
@@ -187,26 +155,6 @@ static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
  */
 static int index_only = 0;
 
-static int git_read_tree(struct tree *tree)
-{
-	int rc;
-	struct object_list *trees = NULL;
-	struct unpack_trees_options opts;
-
-	if (cache_dirty)
-		die("read-tree with dirty cache");
-
-	memset(&opts, 0, sizeof(opts));
-	object_list_append(&tree->object, &trees);
-	rc = unpack_trees(trees, &opts);
-	cache_tree_free(&active_cache_tree);
-
-	if (rc == 0)
-		cache_dirty = 1;
-
-	return rc;
-}
-
 static int git_merge_trees(int index_only,
 			   struct tree *common,
 			   struct tree *head,
@@ -216,11 +164,6 @@ static int git_merge_trees(int index_only,
 	struct object_list *trees = NULL;
 	struct unpack_trees_options opts;
 
-	if (!cache_dirty) {
-		read_cache_from(current_index_file);
-		cache_dirty = 1;
-	}
-
 	memset(&opts, 0, sizeof(opts));
 	if (index_only)
 		opts.index_only = 1;
@@ -236,39 +179,37 @@ static int git_merge_trees(int index_only,
 
 	rc = unpack_trees(trees, &opts);
 	cache_tree_free(&active_cache_tree);
-
-	cache_dirty = 1;
-
 	return rc;
 }
 
+static int unmerged_index(void)
+{
+	int i;
+	for (i = 0; i < active_nr; i++) {
+		struct cache_entry *ce = active_cache[i];
+		if (ce_stage(ce))
+			return 1;
+	}
+	return 0;
+}
+
 static struct tree *git_write_tree(void)
 {
 	struct tree *result = NULL;
 
-	if (cache_dirty) {
-		unsigned i;
-		for (i = 0; i < active_nr; i++) {
-			struct cache_entry *ce = active_cache[i];
-			if (ce_stage(ce))
-				return NULL;
-		}
-	} else
-		read_cache_from(current_index_file);
+	if (unmerged_index())
+		return NULL;
 
 	if (!active_cache_tree)
 		active_cache_tree = cache_tree();
 
 	if (!cache_tree_fully_valid(active_cache_tree) &&
-			cache_tree_update(active_cache_tree,
-				active_cache, active_nr, 0, 0) < 0)
+	    cache_tree_update(active_cache_tree,
+			      active_cache, active_nr, 0, 0) < 0)
 		die("error building trees");
 
 	result = lookup_tree(active_cache_tree->sha1);
 
-	flush_cache();
-	cache_dirty = 0;
-
 	return result;
 }
 
@@ -331,10 +272,7 @@ static struct path_list *get_unmerged(void)
 	int i;
 
 	unmerged->strdup_paths = 1;
-	if (!cache_dirty) {
-		read_cache_from(current_index_file);
-		cache_dirty++;
-	}
+
 	for (i = 0; i < active_nr; i++) {
 		struct path_list_item *item;
 		struct stage_data *e;
@@ -469,9 +407,6 @@ static int remove_file(int clean, const char *path, int no_wd)
 	int update_working_directory = !index_only && !no_wd;
 
 	if (update_cache) {
-		if (!cache_dirty)
-			read_cache_from(current_index_file);
-		cache_dirty++;
 		if (remove_file_from_cache(path))
 			return -1;
 	}
@@ -1105,9 +1040,7 @@ static int merge_trees(struct tree *head,
 		    sha1_to_hex(head->object.sha1),
 		    sha1_to_hex(merge->object.sha1));
 
-	*result = git_write_tree();
-
-	if (!*result) {
+	if (unmerged_index()) {
 		struct path_list *entries, *re_head, *re_merge;
 		int i;
 		path_list_clear(&current_file_set, 1);
@@ -1128,17 +1061,11 @@ static int merge_trees(struct tree *head,
 			if (!process_entry(path, e, branch1, branch2))
 				clean = 0;
 		}
-		if (cache_dirty)
-			flush_cache();
 
 		path_list_clear(re_merge, 0);
 		path_list_clear(re_head, 0);
 		path_list_clear(entries, 1);
 
-		if (clean || index_only)
-			*result = git_write_tree();
-		else
-			*result = NULL;
 	} else {
 		clean = 1;
 		printf("merging of trees %s and %s resulted in %s\n",
@@ -1146,6 +1073,8 @@ static int merge_trees(struct tree *head,
 		       sha1_to_hex(merge->object.sha1),
 		       sha1_to_hex((*result)->object.sha1));
 	}
+	if (index_only)
+		*result = git_write_tree();
 
 	return clean;
 }
@@ -1170,10 +1099,10 @@ static int merge(struct commit *h1,
 		 const char *branch1,
 		 const char *branch2,
 		 int call_depth /* =0 */,
-		 struct commit *ancestor /* =None */,
+		 struct commit_list *ca,
 		 struct commit **result)
 {
-	struct commit_list *ca = NULL, *iter;
+	struct commit_list *iter;
 	struct commit *merged_common_ancestors;
 	struct tree *mrtree;
 	int clean;
@@ -1182,10 +1111,10 @@ static int merge(struct commit *h1,
 	output_commit_title(h1);
 	output_commit_title(h2);
 
-	if (ancestor)
-		commit_list_insert(ancestor, &ca);
-	else
-		ca = reverse_commit_list(get_merge_bases(h1, h2, 1));
+	if (!ca) {
+		ca = get_merge_bases(h1, h2, 1);
+		ca = reverse_commit_list(ca);
+	}
 
 	output("found %u common ancestor(s):", commit_list_count(ca));
 	for (iter = ca; iter; iter = iter->next)
@@ -1211,6 +1140,7 @@ static int merge(struct commit *h1,
 		 * merge_trees has always overwritten it: the commited
 		 * "conflicts" were already resolved.
 		 */
+		discard_cache();
 		merge(merged_common_ancestors, iter->item,
 		      "Temporary merge branch 1",
 		      "Temporary merge branch 2",
@@ -1223,25 +1153,21 @@ static int merge(struct commit *h1,
 			die("merge returned no commit");
 	}
 
+	discard_cache();
 	if (call_depth == 0) {
-		setup_index(0 /* $GIT_DIR/index */);
+		read_cache();
 		index_only = 0;
-	} else {
-		setup_index(1 /* temporary index */);
-		git_read_tree(h1->tree);
+	} else
 		index_only = 1;
-	}
 
 	clean = merge_trees(h1->tree, h2->tree, merged_common_ancestors->tree,
 			    branch1, branch2, &mrtree);
 
-	if (!ancestor && (clean || index_only)) {
+	if (index_only) {
 		*result = make_virtual_commit(mrtree, "merged tree");
 		commit_list_insert(h1, &(*result)->parents);
 		commit_list_insert(h2, &(*result)->parents->next);
-	} else
-		*result = NULL;
-
+	}
 	return clean;
 }
 
@@ -1277,19 +1203,16 @@ static struct commit *get_ref(const char *ref)
 
 int main(int argc, char *argv[])
 {
-	static const char *bases[2];
+	static const char *bases[20];
 	static unsigned bases_count = 0;
 	int i, clean;
 	const char *branch1, *branch2;
 	struct commit *result, *h1, *h2;
+	struct commit_list *ca = NULL;
+	struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
+	int index_fd;
 
 	git_config(git_default_config); /* core.filemode */
-	original_index_file = getenv(INDEX_ENVIRONMENT);
-
-	if (!original_index_file)
-		original_index_file = xstrdup(git_path("index"));
-
-	temporary_index_file = xstrdup(git_path("mrg-rcrsv-tmp-idx"));
 
 	if (argc < 4)
 		die("Usage: %s <base>... -- <head> <remote> ...\n", argv[0]);
@@ -1313,18 +1236,18 @@ int main(int argc, char *argv[])
 	branch2 = better_branch_name(branch2);
 	printf("Merging %s with %s\n", branch1, branch2);
 
-	if (bases_count == 1) {
-		struct commit *ancestor = get_ref(bases[0]);
-		clean = merge(h1, h2, branch1, branch2, 0, ancestor, &result);
-	} else
-		clean = merge(h1, h2, branch1, branch2, 0, NULL, &result);
+	index_fd = hold_lock_file_for_update(lock, get_index_file(), 1);
 
-	if (cache_dirty)
-		flush_cache();
+	for (i = 0; i < bases_count; i++) {
+		struct commit *ancestor = get_ref(bases[i]);
+		ca = commit_list_insert(ancestor, &ca);
+	}
+	clean = merge(h1, h2, branch1, branch2, 0, ca, &result);
+
+	if (active_cache_changed &&
+	    (write_cache(index_fd, active_cache, active_nr) ||
+	     close(index_fd) || commit_lock_file(lock)))
+			die ("unable to write %s", get_index_file());
 
 	return clean ? 0: 1;
 }
-
-/*
-vim: sw=8 noet
-*/