compat: Add simplified merge sort implementation from glibc

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index 753bf50c6dd86a9798e11e096c032e26a8868cca..ff716cabb084526ddb5655c3b7c6dd02f4ed1b39 100755 (executable)
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -92,7 +92,7 @@ USAGE="[--env-filter <command>] [--tree-filter <command>] \
 [--msg-filter <command>] [--commit-filter <command>] \
 [--tag-name-filter <command>] [--subdirectory-filter <directory>] \
 [--original <namespace>] [-d <directory>] [-f | --force] \
-<rev-list options>"
+[<rev-list options>...]"
 
 OPTIONS_SPEC=
 . git-sh-setup
@@ -114,7 +114,6 @@ orig_namespace=refs/original/
 force=
 while :
 do
-       test $# = 0 && usage
        case "$1" in
        --)
                shift
@@ -213,7 +212,7 @@ GIT_WORK_TREE=.
 export GIT_DIR GIT_WORK_TREE
 
 # The refs should be updated if their heads were rewritten
-git rev-parse --no-flags --revs-only --symbolic-full-name "$@" |
+git rev-parse --no-flags --revs-only --symbolic-full-name --default HEAD "$@" |
 sed -e '/^^/d' >"$tempdir"/heads
 
 test -s "$tempdir"/heads ||