tooling: add downstream merge script

The goal for this script is to enable easy importing of upstream code,
which has to be done on a regular basis. The script is intentionally
not placed in the hack/ directory to avoid any conflicts with origin
tooling rebases.

UPSTREAM-MERGE.sh

@@ -0,0 +1,97 @@
+#!/bin/bash
+# This script takes as arguments:
+# $1 - [REQUIRED] upstream version as the first argument to merge
+# $2 - [optional] branch to update, defaults to master. could be a versioned release branch, e.g., release-3.10
+# $3 - [optional] non-openshift remote to pull code from, defaults to upstream
+#
+# Warning: this script resolves all conflicts by overwritting the conflict with
+# the upstream version. If a catalog specific patch was made downstream that is
+# not in the incoming upstream code, the changes will be lost.
+#
+# Origin remote is assumed to point to openshift/service-catalog.
+
+version=$1
+rebase_branch=${2:-master}
+upstream_remote=${3:-upstream}
+
+# sanity checks
+if [[ -z "$version" ]]; then
+  echo "Version argument must be defined."
+  exit 1
+fi
+
+catalog_repo=$(git remote get-url "$upstream_remote")
+if [[ $catalog_repo != "https://github.com/kubernetes-incubator/service-catalog" ]]; then
+  echo "Upstream remote url should be set to kubernetes-incubator repo."
+  exit 1
+fi
+
+# check state of working directory
+git diff-index --quiet HEAD || { printf "!! Git status not clean, aborting !!\\n\\n%s" "$(git status)"; exit 1; }
+
+# update remote, including tags (-t)
+git fetch -t "$upstream_remote"
+
+# do work on the correct branch
+git checkout "$rebase_branch"
+remote_branch=$(git rev-parse --abbrev-ref --symbolic-full-name @{u})
+if [[ $? -ne 0 ]]; then
+  echo "Your branch is not properly tracking upstream as required, aborting."
+  exit 1
+fi
+git merge "$remote_branch"
+git checkout -b "$version"-rebase-"$rebase_branch" || { echo "Expected branch $version-rebase-$rebase_branch to not exist, delete and retry."; exit 1; }
+
+# do the merge, but don't commit so tweaks below are included in commit
+git merge --no-commit tags/"$version"
+
+# get rid of upstream OWNERS, but leave the top level one alone
+find . -mindepth 2 -name OWNERS -exec git rm -f '{}' +
+
+# preserve our version of these files
+git checkout HEAD -- OWNERS Makefile .gitignore
+
+# unmerged files are overwritten with the upstream copy
+unmerged_files=$(git diff --name-only --diff-filter=U --exit-code)
+differences=$?
+if [[ $differences -eq 1 ]]; then
+  unmerged_files_oneline=$(echo "$unmerged_files" | paste -s -d ' ')
+  git checkout --theirs -- $unmerged_files_oneline
+  if [[ $(git diff --check) ]]; then
+    echo "All conflict markers should have been taken care of, aborting."
+    exit 1
+  fi
+  git add -- $unmerged_files_oneline
+else
+  unmerged_files="<NONE>"
+fi
+
+# update upstream Makefile changes, but don't overwrite build patch
+# script executor must manually decline the build patch change, the diff may
+#  contain other changes that need accepting
+git show tags/"$version":Makefile > Makefile.sc
+git add --patch --interactive Makefile.sc
+git checkout Makefile.sc
+
+# bump UPSTREAM-VERSION file
+echo "$version" > UPSTREAM-VERSION
+git add UPSTREAM-VERSION
+
+# just to make sure an old version merge is not being made
+git diff --staged --quiet && { echo "No changed files in merge?! Aborting."; exit 1; }
+
+# make local commit
+git commit -m "Merge upstream tag $version" -m "Merge executed via ./UPSTREAM-MERGE.sh $version $upstream_remote $rebase_branch" -m "$(printf "Overwritten conflicts:\\n%s" "$unmerged_files")"
+
+# verify merge is correct
+git --no-pager log --oneline "$(git merge-base origin/"$rebase_branch" tags/"$version")"..tags/"$version"
+
+printf "\\n** Upstream merge complete! **\\n"
+echo "View the above incoming commits to verify all is well"
+echo "(mirrors the commit listing the PR will show)"
+echo ""
+echo "Now make a pull request, after it's LGTMed make the tag:"
+echo "$ git checkout $rebase_branch
+$ git pull
+$ git tag <origin version>-$version
+$ git push origin <origin version>-$version"