add absorb-repo.sh script

Author: matt-codecov

tools/README.md

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+This directory contains tools for development/maintenance of the codebase itself.
+It should not contain code that needs to be deployed or run in production.

tools/absorb-repo/README.md

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+# `absorb-repo.sh`
+
+This script absorbs a repository into the monorepo in a way that (mostly) preserves its history. History will be rewritten so that the repository's contents will be, or "will have always been", in a subdirectory, but otherwise the authors and dates of each commit will be preserved. Operations like `git blame` can continue past the point where the repository was absorbed.
+
+Example usage:
+```
+$ ./absorb-repo.sh worker [email protected]:codecov/worker.git apps/worker
+```

tools/absorb-repo/absorb-repo.sh

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+#!/bin/sh
+
+# Command line arguments
+repo_name="$1"
+remote_url="$2"
+subdirectory="$3"
+
+# Variables used throughout the script
+local_main_checkout="$repo_name-main"
+absorb_branch="absorb-$repo_name"
+current_branch="$(git rev-parse --abbrev-ref HEAD)"
+
+# Assumes this script's directory has a sibling directory called `git-filter-repo`
+# which contains a copy of the `git-filter-repo` script.
+SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
+GIT_FILTER_REPO_DIR="$(realpath "$SCRIPT_DIR/../git-filter-repo")"
+
+function usage() {
+    echo "Usage:"
+    echo "  $0 <name> <remote-url> <subdirectory>"
+    echo "  Example: $0 worker [email protected]:codecov/worker.git apps/worker"
+    echo ""
+    echo "This script absorbs a repository into the monorepo in a way that (mostly)"
+    echo "preserves its history. History will be rewritten so that the repository's"
+    echo "contents will be, or \"will have always been\", in a subdirectory, but"
+    echo "otherwise the authors and dates of each commit will be preserved. Operations"
+    echo "like \`git blame\` can continue past the point where the repository was"
+    echo "absorbed."
+    echo ""
+    echo "Arguments:"
+    echo "- <name> is the name of the repository you are absorbing. Used to name the git"
+    echo "  remote and the branch used to open a PR."
+    echo ""
+    echo "- <remote-url> must be a valid git remote URL that you have access to. Example:"
+    echo "  \`[email protected]:codecov/worker.git\`"
+    echo ""
+    echo "- <subdirectory> is a path relative to the repository root where <repository>"
+    echo "  should be placed."
+    echo ""
+    echo "This script must be run from inside a git repository."
+    exit 1
+}
+
+if [ $# -ne 3 ] || [ "$(git rev-parse --is-inside-work-tree)" != "true" ]; then
+    usage
+fi
+
+echo "Adding \`$remote_url\` as a remote named \`$repo_name\`..."
+git remote add $repo_name $remote_url
+
+git ls-remote $repo_name | grep main > /dev/null && branch="main" || branch="master"
+git fetch $repo_name $branch
+echo "Found repository with default branch \`$branch\`"
+echo ""
+
+echo "Checking out \`$repo_name/$branch\` locally as \`$local_main_checkout\`..."
+git checkout -b "$local_main_checkout" $repo_name/$branch
+echo "Done"
+echo ""
+
+echo "Rewriting history to put all of $repo_name's contents inside \`$subdirectory\`..."
+# We have to go back to the branch we started on in order to access the `git-filter-repo`
+# custom command.
+git checkout "$current_branch"
+python "$GIT_FILTER_REPO_DIR/git-filter-repo" --force --refs "$local_main_checkout" --to-subdirectory-filter "$subdirectory"
+echo "Done"
+echo ""
+
+echo "Merging the rewritten \`$local_main_checkout\` into our \`$absorb_branch\`"
+git checkout -b $absorb_branch $current_branch
+git merge "$local_main_checkout" --allow-unrelated-histories --no-edit
+echo "Done"
+echo ""
+
+echo "Cleaning up after ourselves..."
+git branch -D $local_main_checkout
+git remote remove $repo_name
+echo "Done"
+
+echo "Pushing to GitHub..."
+git push origin $absorb_branch
+echo "Done. Create a PR!"
+

tools/git-filter-repo/LICENSE

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+Copyright (c) 2009, 2018-2019
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

tools/git-filter-repo/README.md

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+# `git-filter-repo`
+
+Upstream project: https://github.com/newren/git-filter-repo
+
+`git-filter-repo` is a replacement for the stock `git filter-branch` command
+recommended by [the Git project itself](https://git-scm.com/docs/git-filter-branch#_warning).
+
+The copy of the core `git-filter-repo` script included here is not modified.
+
+Usage example:
+```
+# Rewrite the history of `local-worker-main` so that all repository content is placed in `apps/worker`
+$ PATH="$PATH:." git filter-repo --force --refs local-worker-main --to-subdirectory-filter apps/worker
+```