[PATCH 3/8] unpack_trees(): keep track of unmerged entries

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

"git read-tree --reset" will currently remove all unmerged entries in
index before feeding the index to unpack_trees(). Because the lack of
unmerged entries, these entries, when read from tree, will be seen as
"new entries" by {one,two,three}way_merge().

This is fine for now. But for sparse checkout, it needs to know
whether an entry is new entry, because it will handle it different way
than already-in entry.

So the patch moves "unmerged entries removal" part into
unpack_trees(), actually unpack_callback(). The function then can turn
on o->has_unmerged flag, which can be utilized by sparse checkout.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin-read-tree.c |    3 ++-
 unpack-trees.c      |    7 +++++++
 unpack-trees.h      |    2 ++
 3 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/builtin-read-tree.c b/builtin-read-tree.c
index 38fef34..528134c 100644
--- a/builtin-read-tree.c
+++ b/builtin-read-tree.c
@@ -136,9 +136,10 @@ int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)
 			if (stage || opts.merge || opts.prefix)
 				usage(read_tree_usage);
 			opts.reset = 1;
+			opts.prune_unmerged = 1;
 			opts.merge = 1;
 			stage = 1;
-			read_cache_unmerged();
+			read_cache();
 			continue;
 		}
 
diff --git a/unpack-trees.c b/unpack-trees.c
index 83888ae..7d99051 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -301,6 +301,7 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 
 	/* Are we supposed to look at the index too? */
 	if (o->merge) {
+		o->has_unmerged = 0;
 		while (o->pos < o->src_index->cache_nr) {
 			struct cache_entry *ce = o->src_index->cache[o->pos];
 			int cmp = compare_entry(ce, info, p);
@@ -320,6 +321,12 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 						add_entry(o, ce, 0, 0);
 						return mask;
 					}
+
+					if (o->prune_unmerged) {
+						o->has_unmerged = 1;
+						/* leave src[0] as NULL and go over all other staged entries */
+						continue;
+					}
 				}
 				src[0] = ce;
 			}
diff --git a/unpack-trees.h b/unpack-trees.h
index 93ec3c6..86f0989 100644
--- a/unpack-trees.h
+++ b/unpack-trees.h
@@ -43,6 +43,8 @@ struct unpack_trees_options {
 		     verbose_update:1,
 		     aggressive:1,
 		     skip_unmerged:1,
+		     prune_unmerged:1,
+		     has_unmerged:1,
 		     initial_checkout:1,
 		     gently:1;
 	const char *prefix;
-- 
1.6.0.3.890.g95457