[PATCH] Use git-update-ref in scripts.

@@ -108,9 +108,10 @@ fi
 
 tree=$(git-write-tree) || exit 1
 echo Wrote tree $tree
-commit=$(git-commit-tree $tree -p $(cat "$GIT_DIR"/HEAD) < "$final") || exit 1
+parent=$(git-rev-parse --verify HEAD) &&
+commit=$(git-commit-tree $tree -p $parent <"$final") || exit 1
 echo Committed: $commit
-echo $commit > "$GIT_DIR"/HEAD
+git-update-ref HEAD $commit $parent || exit
 
 if test -x "$GIT_DIR"/hooks/post-applypatch
 then

@@ -159,7 +159,9 @@ if [ ! -r "$GIT_DIR/HEAD" ]; then
 		exit 1
 	fi
 	PARENTS=""
+	current=
 else
+	current=$(git-rev-parse --verify HEAD)
 	if [ -f "$GIT_DIR/MERGE_HEAD" ]; then
 		PARENTS="-p HEAD "`sed -e 's/^/-p /' "$GIT_DIR/MERGE_HEAD"`
 	fi

@@ -220,7 +222,7 @@ if test -s .cmitchk
 then
 	tree=$(git-write-tree) &&
 	commit=$(cat .cmitmsg | git-commit-tree $tree $PARENTS) &&
-	echo $commit > "$GIT_DIR/HEAD" &&
+	git-update-ref HEAD $commit $current &&
 	rm -f -- "$GIT_DIR/MERGE_HEAD"
 else
 	echo >&2 "* no commit message?  aborting commit."

@@ -105,14 +105,16 @@ fast_forward_local () {
 	else
 		echo >&2 "* $1: storing $3"
 	fi
-	echo "$2" >"$GIT_DIR/$1" ;;
+	git-update-ref "$1" "$2" 
+	;;
 
     refs/heads/*)
-	# NEEDSWORK: use the same cmpxchg protocol here.
-	echo "$2" >"$GIT_DIR/$1.lock"
-	if test -f "$GIT_DIR/$1"
+	# $1 is the ref being updated.
+	# $2 is the new value for the ref.
+	local=$(git-rev-parse --verify "$1^0" 2>/dev/null)
+	if test "$local"
 	then
-	    local=$(git-rev-parse --verify "$1^0") &&
+	    # Require fast-forward.
 	    mb=$(git-merge-base "$local" "$2") &&
 	    case "$2,$mb" in
 	    $local,*)

@@ -120,34 +122,34 @@ fast_forward_local () {
 		;;
 	    *,$local)
 		echo >&2 "* $1: fast forward to $3"
+		git-update-ref "$1" "$2" "$local"
 		;;
 	    *)
 		false
 		;;
 	    esac || {
 		echo >&2 "* $1: does not fast forward to $3;"
-		case "$force,$single_force" in
-		t,* | *,t)
+		case ",$force,$single_force," in
+		*,t,*)
 			echo >&2 "  forcing update."
+			git-update-ref "$1" "$2" "$local"
 			;;
 		*)
-			mv "$GIT_DIR/$1.lock" "$GIT_DIR/$1.remote"
-			echo >&2 "  leaving it in '$1.remote'"
+			echo >&2 "  not updating."
 			;;
 		esac
 	    }
 	else
-		echo >&2 "* $1: storing $3"
+	    echo >&2 "* $1: storing $3"
+	    git-update-ref "$1" "$2"
 	fi
-	test -f "$GIT_DIR/$1.lock" &&
-	    mv "$GIT_DIR/$1.lock" "$GIT_DIR/$1"
 	;;
     esac
 }
 
 case "$update_head_ok" in
 '')
-	orig_head=$(cat "$GIT_DIR/HEAD" 2>/dev/null)
+	orig_head=$(git-rev-parse --verify HEAD 2>/dev/null)
 	;;
 esac
 

@@ -184,7 +186,7 @@ do
     rsync://*)
 	TMP_HEAD="$GIT_DIR/TMP_HEAD"
 	rsync -L -q "$remote/$remote_name" "$TMP_HEAD" || exit 1
-	head=$(git-rev-parse TMP_HEAD)
+	head=$(git-rev-parse --verify TMP_HEAD)
 	rm -f "$TMP_HEAD"
 	test "$rsync_slurped_objects" || {
 	    rsync -av --ignore-existing --exclude info \

@@ -261,10 +263,10 @@ case ",$update_head_ok,$orig_head," in
 *,, | t,* )
 	;;
 *)
-	curr_head=$(cat "$GIT_DIR/HEAD" 2>/dev/null)
+	curr_head=$(git-rev-parse --verify HEAD 2>/dev/null)
 	if test "$curr_head" != "$orig_head"
 	then
-		echo "$orig_head" >$GIT_DIR/HEAD
+	    	git-update-ref HEAD "$orig_head"
 		die "Cannot fetch into the current branch."
 	fi
 	;;

@@ -114,8 +114,9 @@ case "$#,$common" in
 	# Again the most common case of merging one remote.
 	echo "Updating from $head to $1."
 	git-update-index --refresh 2>/dev/null
-	git-read-tree -u -m $head "$1" || exit 1
-	git-rev-parse --verify "$1^0" > "$GIT_DIR/HEAD"
+	git-read-tree -u -m $head "$1" &&
+	new_head=$(git-rev-parse --verify "$1^0") &&
+	git-update-ref HEAD "$new_head" "$head" || exit 1
 	summary "$1"
 	dropsave
 	exit 0

@@ -218,9 +219,9 @@ then
     do
         parents="$parents -p $remote"
     done
-    result_commit=$(echo "$merge_msg" | git-commit-tree $result_tree $parents)
+    result_commit=$(echo "$merge_msg" | git-commit-tree $result_tree $parents) || exit
     echo "Committed merge $result_commit, made by $wt_strategy."
-    echo $result_commit >"$GIT_DIR/HEAD"
+    git-update-ref HEAD $result_commit $head
     summary $result_commit
     dropsave
     exit 0

@@ -86,5 +86,5 @@ esac
 result_commit=$(git-fmt-merge-msg <"$GIT_DIR/FETCH_HEAD" |
 		git-commit-tree $MRT $PARENT)
 echo "Committed merge $result_commit"
-echo $result_commit >"$GIT_DIR"/HEAD
+git-update-ref HEAD $result_commit $head
 git-diff-tree -p $head $result_commit | git-apply --stat

@@ -6,10 +6,10 @@
 
 . git-sh-setup || die "Not a git archive"
 
-orig_head=$(cat "$GIT_DIR/HEAD") || die "Pulling into a black hole?"
+orig_head=$(git-rev-parse --verify HEAD) || die "Pulling into a black hole?"
 git-fetch --update-head-ok "$@" || exit 1
 
-curr_head=$(cat "$GIT_DIR/HEAD")
+curr_head=$(git-rev-parse --verify HEAD)
 if test "$curr_head" != "$orig_head"
 then
 	# The fetch involved updating the current branch.

@@ -38,4 +38,4 @@ case "$merge_head" in
 esac
 
 merge_name=$(git-fmt-merge-msg <"$GIT_DIR/FETCH_HEAD")
-git-resolve "$(cat "$GIT_DIR"/HEAD)" $merge_head "$merge_name"
+git-resolve "$curr_head" $merge_head "$merge_name"

@@ -33,7 +33,8 @@ test "$different1$different2" = "" ||
 die "Your working tree does not match $ours_symbolic."
 
 git-read-tree -m -u $ours $upstream &&
-git-rev-parse --verify "$upstream^0" >"$GIT_DIR/HEAD" || exit
+new_head=$(git-rev-parse --verify "$upstream^0") &&
+git-update-ref HEAD "$new_head" || exit
 
 tmp=.rebase-tmp$$
 fail=$tmp-fail

@@ -50,7 +51,7 @@ do
 		continue ;;
 	esac
 	echo >&2 "* Applying: $msg"
-	S=`cat "$GIT_DIR/HEAD"` &&
+	S=$(git-rev-parse --verify HEAD) &&
 	git-cherry-pick --replay $commit || {
 		echo >&2 "* Not applying the patch and continuing."
 		echo $commit >>$fail

@@ -60,7 +60,7 @@ then
 else
 	rm -f "$GIT_DIR/ORIG_HEAD"
 fi
-echo "$rev" >"$GIT_DIR/HEAD"
+git-update-ref HEAD "$rev"
 
 case "$reset_type" in
 --hard )

@@ -45,7 +45,7 @@ case "$common" in
 "$head")
 	echo "Updating from $head to $merge."
 	git-read-tree -u -m $head $merge || exit 1
-	echo $merge > "$GIT_DIR"/HEAD
+	git-update-ref HEAD "$merge"
 	git-diff-tree -p $head $merge | git-apply --stat
 	dropheads
 	exit 0

@@ -99,6 +99,6 @@ if [ $? -ne 0 ]; then
 fi
 result_commit=$(echo "$merge_msg" | git-commit-tree $result_tree -p $head -p $merge)
 echo "Committed merge $result_commit"
-echo $result_commit > "$GIT_DIR"/HEAD
+git-update-ref HEAD "$result_commit"
 git-diff-tree -p $head $result_commit | git-apply --stat
 dropheads

@@ -13,6 +13,8 @@
 static int merge = 0;
 static int update = 0;
 static int index_only = 0;
+static int nontrivial_merge = 0;
+static int trivial_merges_only = 0;
 
 static int head_idx = -1;
 static int merge_size = 0;

@@ -275,6 +277,9 @@ static int unpack_trees(merge_fn_t fn)
 	if (unpack_trees_rec(posns, len, "", fn, &indpos))
 		return -1;
 
+	if (trivial_merges_only && nontrivial_merge)
+		die("Merge requires file-level merging");
+
 	check_updates(active_cache, active_nr);
 	return 0;
 }

@@ -460,6 +465,8 @@ static int threeway_merge(struct cache_e
 		verify_uptodate(index);
 	}
 
+	nontrivial_merge = 1;
+
 	/* #2, #3, #4, #6, #7, #9, #11. */
 	count = 0;
 	if (!head_match || !remote_match) {

@@ -629,9 +636,15 @@ int main(int argc, char **argv)
 			continue;
 		}
 
+		if (!strcmp(arg, "--trivial")) {
+			trivial_merges_only = 1;
+			continue;
+		}
+
 		if (!strcmp(arg, "--head")) {
 			head_idx = stage - 1;
 			fn = threeway_merge;
+			continue;
 		}
 
 		/* "-m" stands for "merge", meaning we start in stage 1 */