Re: git-add fails after file type change

When replacing an existing file A with a directory B that has a
file B/C in it in the index, 'update-index --replace --add B/C'
did not properly remove the file to make room for the new
directory.

There was a trivial logic error, most likely a cut & paste one,
dating back to quite early days of git.

Signed-off-by: Junio C Hamano <redacted>
---

  Junio C Hamano [off-list ref] writes:

  > But I think you helped me to spot a bug ;-).
  >
  >         $ git update-index --replace --add 3/2
  >         $ git ls-files -s
  >         100644 00750edc07d6415dcc07ae0351e9397b0222b7ba 0     1
  >         100644 00750edc07d6415dcc07ae0351e9397b0222b7ba 0     3
  >         100644 fa457baf8abbf5dd3bb4cbfab0c5a4cf0523d7f8 0     3/2
  >
  > The entry '3' should have been removed when we did --replace.
  > This index cannot be written out as a tree:
  >
  >       $ git write-tree
  >         You have both 3 and 3/2
  >         fatal: git-write-tree: error building trees

  And this fixes it.

 read-cache.c     |    2 +-
 t/t0000-basic.sh |    9 +++++++++
 2 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/read-cache.c b/read-cache.c
index a602010..e856a2e 100644
--- a/read-cache.c
+++ b/read-cache.c

@@ -517,7 +517,7 @@ static int has_dir_name(const struct cache_entry *ce, int pos, int ok_to_replace
 		pos = cache_name_pos(name, ntohs(create_ce_flags(len, stage)));
 		if (pos >= 0) {
 			retval = -1;
-			if (ok_to_replace)
+			if (!ok_to_replace)
 				break;
 			remove_cache_entry_at(pos);
 			continue;

diff --git a/t/t0000-basic.sh b/t/t0000-basic.sh
index 3260d1d..0cd1c41 100755
--- a/t/t0000-basic.sh
+++ b/t/t0000-basic.sh

@@ -272,4 +272,13 @@ test_expect_success \
 	 wc -l) &&
      test $numparent = 1'
 
+test_expect_success 'update-index D/F conflict' '
+	mv path0 tmp &&
+	mv path2 path0 &&
+	mv tmp path2 &&
+	git update-index --add --replace path2 path0/file2 &&
+	numpath0=$(git ls-files path0 | wc -l) &&
+	test $numpath0 = 1
+'
+
 test_done