PROTOTYPE: Magic files to access search results/modified files

Created by: mrnugget

NOTE FOR REVIEWERS: This is a prototype and should be treated as such, which means: let's review idea/design/feasibility instead of concrete implementation details (but if you do have concrete feedback on the implementation, feel free to leave it as such).

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This is another prototype, next to https://github.com/sourcegraph/src-cli/pull/334, to solve the same thing: allowing step.run commands to access specific files.

What this prototype does is to create magic files inside the container. The files contain lists of files, one filename per line. By using standard shell scripting, the run commands can then access these files.

Example campaign spec:

name: a-magic-file-appeared
description: Updated description Hello World to READMEs

on:
  - repositoriesMatchingQuery: lang:go fmt.Sprintf("%d", :[v]) patterntype:structural -file:vendor repo:automation-testing

steps:
  # The two magic files right now are:
  #
  #   /src/search-results                contains search results in current repository, one per line
  #   /src/previous-step/modified-files  contains files modified by previous step, one per line
  #
  # How do you make use of them?
  #
  # Option 1) Use a loop:
  - run: cat /src/search-results | while read result; do xargs comby -in-place 'fmt.Sprintf("%d", :[v])' 'strconv.Itoa(:[v])' "${result}"; done
    container: comby/comby
  # Option 2) Use cat, which Unix-snobs say is useless here:
  - run: cat /src/search-results | xargs comby -in-place 'fmt.Sprintf("%d", :[v])' 'strconv.Itoa(:[v])' 
    container: comby/comby
  # Option 3) The Unix-snobs-approved variant: use the file as STDIN
  - run: </src/search-results xargs comby -in-place 'fmt.Sprintf("%d", :[v])' 'strconv.Itoa(:[v])' 
    container: comby/comby
  # We just ran comby three times. Now let's use `goimports` to format the modified files:
  - run: cat /src/previous-step/modified-files | xargs goimports -w
    container: unibeautify/goimports

# [...]

Screenshot

Details

This branch here builds on top of https://github.com/sourcegraph/src-cli/pull/334. But instead of using templating, it simply makes the data available in temp files that are then mounted into the container.

Drawbacks

• shell scripting required. It's not super advanced, but it also might not be as straightforward as the templating approach.