Merge branch 'jk/checkout-from-tree'

"git checkout $treeish $path", when $path in the index and the
working tree already matched what is in $treeish at the $path,
still overwrote the $path unnecessarily.

* jk/checkout-from-tree:
  checkout $tree: do not throw away unchanged index entries

1 files changed, 18 insertions, 0 deletions

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 5410dac..5a78758 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -67,6 +67,7 @@ static int update_some(const unsigned char *sha1, const char *base, int baselen,
 {
 	int len;
 	struct cache_entry *ce;
+	int pos;
 
 	if (S_ISDIR(mode))
 		return READ_TREE_RECURSIVE;
@@ -79,6 +80,23 @@ static int update_some(const unsigned char *sha1, const char *base, int baselen,
 	ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
 	ce->ce_namelen = len;
 	ce->ce_mode = create_ce_mode(mode);
+
+	/*
+	 * If the entry is the same as the current index, we can leave the old
+	 * entry in place. Whether it is UPTODATE or not, checkout_entry will
+	 * do the right thing.
+	 */
+	pos = cache_name_pos(ce->name, ce->ce_namelen);
+	if (pos >= 0) {
+		struct cache_entry *old = active_cache[pos];
+		if (ce->ce_mode == old->ce_mode &&
+		    !hashcmp(ce->sha1, old->sha1)) {
+			old->ce_flags |= CE_UPDATE;
+			free(ce);
+			return 0;
+		}
+	}
+
 	add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
 	return 0;
 }