work around an obnoxious bash "safety feature" on OpenBSD

Bash (4.0.24) on OpenBSD 4.6 refuses to run this snippet:

    $ cat gomi.sh
    #!/bin/sh
    one="/var/tmp/1 1"
    rm -f /var/tmp/1 "/var/tmp/1 1"
    echo hello >$one
    $ sh gomi.sh; ls /var/tmp/1*
    /var/tmp/1 1
    $ bash gomi.sh; ls /var/tmp/1*
    gomi.sh: line 4: $one: ambiguous redirect
    ls: /var/tmp/1*: No such file or directory

Every competent shell programmer knows that a <$word in redirection is not
subject to field splitting (POSIX.1 "2.7 Redirection" explicitly lists the
kind of expansion performed: "... the word that follows the redirection
operator shall be subjected to ...", and "Field Splitting" is not among
them).

Some clueless folks apparently decided that users need to be protected in
the name of "security", however.

Output from "git grep -e '> *\$' -- '*.sh'" indicates that rebase-i
suffers from this bogus "safety".  Work it around by surrounding the
variable reference with a dq pair.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-rebase--interactive.sh

@@ -378,7 +378,7 @@ update_squash_messages () {
 			sed -e 1d -e '2,/^./{
 				/^$/d
 			}' <"$SQUASH_MSG".bak
-		} >$SQUASH_MSG
+		} >"$SQUASH_MSG"
 	else
 		commit_message HEAD > "$FIXUP_MSG" || die "Cannot write $FIXUP_MSG"
 		COUNT=2
@@ -387,7 +387,7 @@ update_squash_messages () {
 			echo "# The first commit's message is:"
 			echo
 			cat "$FIXUP_MSG"
-		} >$SQUASH_MSG
+		} >"$SQUASH_MSG"
 	fi
 	case $1 in
 	squash)
@@ -403,7 +403,7 @@ update_squash_messages () {
 		echo
 		commit_message $2 | sed -e 's/^/#	/'
 		;;
-	esac >>$SQUASH_MSG
+	esac >>"$SQUASH_MSG"
 }
 
 peek_next_command () {