Improve do-release script

do-release.bash

@@ -1,17 +1,63 @@
 #!/bin/bash
 
-if [[ $# -lt 1 ]] || [[ $# -gt 3 ]]; then
-  echo "usage: $0 <release-version> [--force] [--dry-run]"
+if [[ "$DEBUG" == 1 ]]; then
+  set -x
+fi
+
+usage() {
+  echo "usage: $0 <release-version> [--amend] [--force] [--dry-run]"
   exit 1
+}
+
+if [[ $# -lt 1 ]]; then
+  usage
 fi
 
-if [[ " $@ " =~ " --force " ]] && ! git diff-files --quiet; then
+RELEASE="$1"
+COMMIT_FLAGS=""
+TAG_FLAGS=""
+PUSH_FLAGS=""
+NO_DIRTY=1
+AMEND=0
+shift
+
+for arg; do
+  case "$arg" in
+    --force)
+      TAG_FLAGS="$TAG_FLAGS --force"
+      PUSH_FLAGS="$PUSH_FLAGS --force"
+      NO_DIRTY=0
+      ;;
+
+    --dry-run)
+      PUSH_FLAGS="$PUSH_FLAGS --dry-run"
+      ;;
+
+    --amend)
+      COMMIT_FLAGS="$COMMIT_FLAGS --amend"
+      TAG_FLAGS="$TAG_FLAGS --force"
+      PUSH_FLAGS="$PUSH_FLAGS --force"
+      AMEND=1
+      ;;
+
+    *)
+      usage
+      ;;
+  esac
+done
+
+if [[ "$NO_DIRTY" == "1" ]] && ! git diff-files --quiet; then
   echo "dirty working tree, commit changes"
   exit 1
 fi
 
 set -e
 
+if [[ "$AMEND" == "1" ]] && ! git show -s --format=%B | grep --quiet "^LATEST_"; then
+  echo "can only amend release commit"
+  exit 1
+fi
+
 echo "Edit changeset:"
 if which editor &>/dev/null; then
   editor RELEASE.md
@@ -29,20 +75,22 @@ cat Makefile.versions.mk
 echo "Adding changes..."
 git add RELEASE.md Makefile.versions.mk
 
-echo "Committing $1..."
-cat <<EOF | git commit -F -
-v$1
+echo "Creating temporary branch..."
+git checkout $(git rev-parse HEAD) >/dev/null
+
+echo "Committing $RELEASE..."
+cat <<EOF | git commit $COMMIT_FLAGS -F -
+v$RELEASE
 
 $(cat Makefile.versions.mk)
 EOF
 
-if [[ " $@ " =~ " --force " ]]; then
-  git tag "$1" -f
-else
-  git tag "$1"
-fi
+git tag "$RELEASE" $TAG_FLAGS
+
+echo "Checking master again..."
+git checkout "master"
 
 echo "Pushing..."
-git push origin "master" "$@"
+git push origin "$RELEASE" $PUSH_FLAGS
 
 echo "Done."