batches: Mount paths into a container

Created by: Piszmog

Closes #31790.

Add the ability to mount a path on the local machine into a container during a step.

A path can point to a file (./foo.sh or /bar/foo.sh) or a directory (./bar or /foo/bar/). The path can be an absolute path or a relative path (for example ./foo.sh). Regardless if the path is absolute or relative, the path must be within the same directory as the batch spec that is being ran (the batch spec directory is considered the "working directory").

Validation/handling of the mount field in a step is handled in the src-cli versus batcheslib in sourcegraph/sourcegraph. The reason for this was the avoid having conditional logic to figure out if parseBatchSpec is being called on a local machine vs behind an API. This also contains the file system logic within the context of src-cli which is dealing with the file system.

This PR also includes some general fixes I saw while in the code (for example, package and variable naming collision).

Test plan

Go Unit Tests and manual testing.

Examples

Below are examples of mounting a path that contains a script (python or Go binary in this case) that is ran in the run field of a step.

Python

Example of running a python script that is mounted into the container and ran in a step.

Batch Spec

name: python-script-test
description: Use a python script
on:
  - repositoriesMatchingQuery: file:README.md
steps:
  - run: python /tmp/updater.py
    container: python:latest
    mount:
      - path: ./updater.py
        mountpoint: /tmp/updater.py
changesetTemplate:
  title: Hello from Python
  body: Updated using a Python Script
  branch: python-script-test
  commit:
    message: Append Hello World to all README.md files

Script

#!/usr/bin/env python3
import os.path


def main():
    exists = os.path.exists('README.md')
    if exists:
        with open('README.md', 'a') as f:
            f.write('\nHello from python')


if __name__ == "__main__":
    main()

Changesets

Binary

Example of running a binary (written in Go) that is mounted into the container and ran in a step.

Batch Spec

name: binary-test
description: Use a binary
on:
  - repositoriesMatchingQuery: file:README.md
steps:
  - run: /tmp/updater
    container: alpine:latest
    mount:
      - path: ./updater # the linux binary
        mountpoint: /tmp/updater
changesetTemplate:
  title: Hello from a binary
  body: Updated using a binary
  branch: binary-test
  commit:
    message: Append Hello World to all README.md files

Binary

Binary was built from Go

package main

import "os"

func main() {
	fileInfo, err := os.Stat("README.md")
	if err != nil {
		panic(err)
	}
	if fileInfo.IsDir() {
		panic("file is a directory")
	}

	f, err := os.OpenFile("README.md", os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		panic(err)
	}
	defer f.Close()

	if _, err = f.WriteString("\nhello from go"); err != nil {
		panic(err)
	}
}

Built with the following command,

env GOOS=linux GOGOARCH=amd64 go build -ldflags="-s -w"

Changesets

Directory

The above examples have the path pointing to a specific file. Directories can also be mounted in the container. This example reuses the above Python Example but mounts a directory that contains the script.

Batch Spec

name: python-script-test
description: Use a python script
on:
  - repositoriesMatchingQuery: file:README.md
steps:
  - run: python /tmp/scripts/updater.py
    container: python:latest
    mount:
      - path: ./scripts
        mountpoint: /tmp/scripts
changesetTemplate:
  title: Hello from Python
  body: Updated using a Python Script
  branch: python-script-test
  commit:
    message: Append Hello World to all README.md files

Changesets