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cleanup: make an empty commit for actions/checkout
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Make an empty detached commit for actions/checkout to properly
clean the project's workspace before checking out new code
revision.

Part of #28
Related to tarantool/tarantool-qa#145
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NickVolynkin committed Nov 10, 2022
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54 changes: 46 additions & 8 deletions cleanup/README.md
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# Setup environment

Action cleans workspace directory after previous run. The main reason to add
this action is [tarantool/tarantool-qa#145](https://github.com/tarantool/tarantool-qa/issues/145).
When submodules are changed, the standard checkout fails with git errors.
It's a well-known problem and the related issue
[actions/checkout#418](https://github.com/actions/checkout/issues/418) is still opened.
Action creates an empty detached commit, which helps subsequent
[actions/checkout](https://github.com/actions/checkout) action
correctly clean the workspace.

## How to use GitHub Action from GitHub workflow
## Usage

Add the following code to the running steps before `checkout` action:
Add the following line to your workflow before the `actions/checkout` action:
```diff
+ - uses: tarantool/actions/cleanup@master
- uses: actions/checkout@v3
...
```
- uses: tarantool/actions/cleanup@master

## Explanation and rationale

The main reason to add
this action is [tarantool/tarantool-qa#145](https://github.com/tarantool/tarantool-qa/issues/145).
When submodules change, actions/checkout fails with git errors.
It's a well-known problem and the related issues are still open:
actions/checkout#354,
actions/checkout#385,
actions/checkout#418, and
actions/checkout#590.

Before checking out a new revision, actions/checkout runs the following code:

```bash
# removes ignored and non-versioned files
git clean -ffdx
# resets workspace to the commit, on which it was left
# after the last job run
git reset --hard
```

The problem is that when a workflow fails because of a particular commit,
the repository still stays on that commit. On the next job run,
actions/checkout will run the above code, restore that particular commit,
and fail to make a proper code checkout.

By creating a detached empty commit, this actions forces actions/checkout
to clean up the project's workspace entirely, removing any files that could
break checkout. Meanwhile, the `.git` directory stays intact, so full checkout
isn't required and the workflow doesn't waste much time.

If this is a first job run on a particular runner and there's no repository yet,
the command in this action will silently fail, thanks to `|| :`,
but the action itself will succeed.

This action uses a solution proposed in a
[comment](https://github.com/actions/checkout/issues/590#issuecomment-970586842) at actions/checkout#590.
7 changes: 5 additions & 2 deletions cleanup/action.yml
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---
name: 'Clean workspace'
description: 'Clean workspace directory after previous workflow run'
description: 'Clean workspace directory by making an empty detached commit'
runs:
using: 'composite'
steps:
- run: |
set -e
shopt -s dotglob
rm -rf ${{ github.workspace }}/*
git checkout -f \
$(git -c user.name=TarantoolBot -c [email protected] commit-tree \
$(git hash-object -t tree /dev/null) -m 'empty commit' \
< /dev/null) || :
shell: bash

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