merge-one-file: fix broken merges with alternate work trees

diff --git a/git-merge-one-file.sh b/git-merge-one-file.sh
index 9c2c1b7202462370509a7bdb391982ae32564bd6..bb64a72ad3b8db6f43fafc5af87a1697b4bf2989 100755 (executable)
--- a/git-merge-one-file.sh
+++ b/git-merge-one-file.sh
@@ -16,6 +16,23 @@
 # been handled already by git read-tree, but that one doesn't
 # do any merges that might change the tree layout.
 
+USAGE='<orig blob> <our blob> <their blob> <path>'
+USAGE="$USAGE <orig mode> <our mode> <their mode>"
+LONG_USAGE="Usage: git merge-one-file $USAGE
+
+Blob ids and modes should be empty for missing files."
+
+SUBDIRECTORY_OK=Yes
+. git-sh-setup
+cd_to_toplevel
+require_work_tree
+
+if ! test "$#" -eq 7
+then
+       echo "$LONG_USAGE"
+       exit 1
+fi
+
 case "${1:-.}${2:-.}${3:-.}" in
 #
 # Deleted in both or deleted in one and unchanged in the other
@@ -120,7 +137,7 @@ case "${1:-.}${2:-.}${3:-.}" in
 
        # Create the working tree file, using "our tree" version from the
        # index, and then store the result of the merge.
-       git checkout-index -f --stage=2 -- "$4" && cat "$src1" >"$4"
+       git checkout-index -f --stage=2 -- "$4" && cat "$src1" >"$4" || exit 1
        rm -f -- "$orig" "$src1" "$src2"
 
        if [ "$6" != "$7" ]; then