apply: get rid of --index-info in favor of --build-fake-ancestor

git-am used "git apply -z --index-info" to find the original versions
of the files touched by the diff, to be able to do an inexpensive
three-way merge.

This operation makes only sense in a repository, since the index
information in the diff refers to blobs, which have to be present in
the current repository.

Therefore, teach "git apply" a mode to write out the result as an
index file to begin with, obviating the need for scripts to do it
themselves.

The sole user for --index-info is "git am" is converted to
use --build-fake-ancestor in this patch.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 4 deletions

diff --git a/git-am.sh b/git-am.sh
index b66173c0c..32c46d7ed 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -62,10 +62,8 @@ fall_back_3way () {
     mkdir "$dotest/patch-merge-tmp-dir"
 
     # First see if the patch records the index info that we can use.
-    git apply -z --index-info "$dotest/patch" \
-	>"$dotest/patch-merge-index-info" &&
-    GIT_INDEX_FILE="$dotest/patch-merge-tmp-index" \
-    git update-index -z --index-info <"$dotest/patch-merge-index-info" &&
+    git apply --build-fake-ancestor "$dotest/patch-merge-tmp-index" \
+	"$dotest/patch" &&
     GIT_INDEX_FILE="$dotest/patch-merge-tmp-index" \
     git write-tree >"$dotest/patch-merge-base+" ||
     cannot_fallback "Repository lacks necessary blobs to fall back on 3-way merge."