1 files changed, 76 insertions, 0 deletions
diff --git a/git-checkout.sh b/git-checkout.sh
new file mode 100755
index 000000000..4e7c57a5f
--- /dev/null
+++ b/git-checkout.sh
@@ -0,0 +1,76 @@
+#!/bin/sh
+. git-sh-setup || die "Not a git archive"
+
+old=$(git-rev-parse HEAD)
+new=
+force=
+branch=
+newbranch=
+while [ "$#" != "0" ]; do
+    arg="$1"
+    shift
+    case "$arg" in
+	"-b")
+		newbranch="$1"
+		shift
+		[ -z "$newbranch" ] &&
+			die "git checkout: -b needs a branch name"
+		[ -e "$GIT_DIR/refs/heads/$newbranch" ] &&
+			die "git checkout: branch $newbranch already exists"
+		;;
+	"-f")
+		force=1
+		;;
+	*)
+		rev=$(git-rev-parse --verify "$arg^0") || exit
+		if [ -z "$rev" ]; then
+			echo "unknown flag $arg"
+			exit 1
+		fi
+		if [ "$new" ]; then
+			echo "Multiple revisions?"
+			exit 1
+		fi
+		new="$rev"
+		if [ -f "$GIT_DIR/refs/heads/$arg" ]; then
+			branch="$arg"
+		fi
+		;;
+    esac
+done
+[ -z "$new" ] && new=$old
+
+#
+# If we don't have an old branch that we're switching to,
+# and we don't have a new branch name for the target we
+# are switching to, then we'd better just be checking out
+# what we already had
+#
+[ -z "$branch$newbranch" ] &&
+	[ "$new" != "$old" ] &&
+	die "git checkout: you need to specify a new branch name"
+
+if [ "$force" ]
+then
+    git-read-tree --reset $new &&
+	git-checkout-index -q -f -u -a
+else
+    git-read-tree -m -u $old $new
+fi
+
+# 
+# Switch the HEAD pointer to the new branch if it we
+# checked out a branch head, and remove any potential
+# old MERGE_HEAD's (subsequent commits will clearly not
+# be based on them, since we re-set the index)
+#
+if [ "$?" -eq 0 ]; then
+	if [ "$newbranch" ]; then
+		echo $new > "$GIT_DIR/refs/heads/$newbranch"
+		branch="$newbranch"
+	fi
+	[ "$branch" ] && ln -sf "refs/heads/$branch" "$GIT_DIR/HEAD"
+	rm -f "$GIT_DIR/MERGE_HEAD"
+else
+	exit 1
+fi