Add a script for rebasing crate branches

scripts/rebase.sh

@@ -0,0 +1,40 @@
+#!/bin/bash
+
+set -e
+
+cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.."
+
+if ! git diff-index --quiet HEAD; then
+    echo "Not running rebase.sh because git working directory is dirty" >&2
+    exit 1
+fi
+
+if [ -z "$1" ]; then
+    echo "Usage: scripts/rebase.sh [crate]..." >&2
+    exit 1
+fi
+
+base=$(git rev-parse HEAD)
+push=()
+
+(
+    set -x
+    git fetch --quiet origin --tags
+)
+
+for crate in "$@"; do
+    (
+        set -x
+        git tag -d "$crate" &>/dev/null || true
+        git checkout --quiet origin/"$crate"
+        git rebase --quiet "$base"
+    )
+    push+=("$(git rev-parse HEAD):refs/heads/$crate")
+done
+
+(
+    set -x
+    git checkout --quiet "$base"
+)
+
+git push origin --force-with-lease "${push[@]}"