Build block for srclibs

The idea behind

Some thoughts that came together:

• some srclibs need to build something, e.g. an .aar file
  • currently these build "recipes" are located in the app metadata
  • sometimes these artifacts are build multiple times if multiple apps need them
• sometimes different versions of srclibs need to be treated differently
  • e.g. VLC already has multiple srclib.yml files

Pro and Con

Pro

• if there is something to build it dosn't have to build twice → saves build server time
• a place for scanignore/scandelete → #784

Con

• Cost of developer time

Proposed format

Pretty much like app metadata, but without versionName, versionCodeetc.
Regarding updates I would suggest updating them manually, so no AutoUpdateMode etc.

There should be one entry in Builds that has default: true and will be used when the wanted version (the thing behind the '@') is not an entry in the Builds block.

Artifacts

Handling these is an important point; here are some options:

# srclib.yml
Builds:
  - artifacts: true

This will keep the whole cloned (and prepared) repository. Usage in app metadata as usual.

# srclib.yml
Builds:
  - artifacts: false

This will not keep any files. The srclib will be cloned, prepared etc. every time needed. Usage in app metadata as usual again.

# srclib.yml
Builds:
  - artifacts:
      - directory
      - file.txt
      - directory/subdir/file1.txt

This will keep the specified files. They can be accessed in the app metadata with $$srclib$$[i] where i is the index of artifacts array. [This will require a lookup for the actual order in srclib.yml in the implementation.]

Example

fdroid_fdroidserver.yml

RepoType: git
Repo: https://gitlab.com/fdroid/fdroidserver.git

Builds:
  - commit: ea9f917ddc95bf766320229fa2cc36db0cfc850a
    build:
      - echo "Some command …"
      - echo "… and another command."
    artifacts:
      - abc
      - abc/def/ghi.aar
  - default: true
    rm: README.md

Proposed Workflow

Could happen at that time a Prepare would.

graph TD
START["An app requires srclib aprilfools@1337."]
START --> QBUILT(["Has version '1337' already been prepared/built?"])
QBUILT -->|Yes.|BUILTYES("Pull the artifact(s) in and use them!")
QBUILT -->|No.|BUILTNO("Prepare/build this version of the srclib!")
BUILTNO --> QINBUILDS(["Is version '1337' in 'Builds'?"])
QINBUILDS --> |Yes.|INBUILDSYES("Use their build block!")
QINBUILDS --> |No.|INBUILDSNO("Use the 'default' block!")
INBUILDSYES --> END("Build or prepare the srclib!")
INBUILDSNO --> END

Open points

• Where to save the artifacts? Similar to unsigned apks?
• Garbage collections for those that were not used for a while?
• Lint for srclib.yml files?
• What about the "old" format?

Feel free to add some more!