am --abort: support aborting to unborn branch

When git-am is first run on an unborn branch, no ORIG_HEAD is created.
As such, any applied commits will remain even after a git am --abort.

To be consistent with the behavior of git am --abort when it is not run
from an unborn branch, we empty the index, and then destroy the branch
pointed to by HEAD if there is no ORIG_HEAD.

Signed-off-by: Paul Tan <pyokagan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/git-am.sh b/git-am.sh
index f71d7bb997..1e4770ad71 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -514,7 +514,14 @@ then
 			index_tree=$(git write-tree) &&
 			orig_head=$(git rev-parse --verify -q ORIG_HEAD || echo $empty_tree) &&
 			git read-tree -m -u $index_tree $orig_head
-			git reset ORIG_HEAD
+			if git rev-parse --verify -q ORIG_HEAD >/dev/null 2>&1
+			then
+				git reset ORIG_HEAD
+			else
+				git read-tree $empty_tree
+				curr_branch=$(git symbolic-ref HEAD 2>/dev/null) &&
+				git update-ref -d $curr_branch
+			fi
 		fi
 		rm -fr "$dotest"
 		exit ;;