Feature: Allow building offline

[glensc]

What are you trying to do?

I'd like to separate the download phase from the build/install phase so that extension installation can be performed without network access.

This is useful for Docker/BuildKit builds where only specific build steps are allowed network access. For example:

1. Download all required artifacts while networking is enabled.
2. Disable networking (RUN --network=none).
3. Build and install the extension entirely from the previously downloaded artifacts.

This is similar to how package managers like apt support --download-only and --no-download.

What platform, and PIE version are you using?

pie show -v
🥧 PHP Installer for Extensions (PIE) 1.4.9, from The PHP Foundation
You are running PHP 8.3.33
Target PHP installation: 8.3.33 nts, on Linux/OSX/etc x86_64 (from /usr/bin/php8.3)
Using pie.json: /root/.config/pie/php8.3_8e7fcd745470cd568cb685b6efc26480/pie.json
Using pie.json: /root/.config/pie/php8.3_8e7fcd745470cd568cb685b6efc26480/pie.json
Tip: to include extensions in this list that PIE does not manage, use the --all flag.

Loaded PIE extensions:
(none)

Steps to reproduce the issue

Currently the only available workflow is:

pie install phalcon/cphalcon:5.17.0

This combines:

• dependency resolution
• metadata retrieval
• downloading
• building
• installation

There doesn't appear to be a way to perform the download separately and later install using only locally cached artifacts.

What do you expect to happen?

It would be great if PIE supported an offline-friendly workflow, for example:

pie download phalcon/cphalcon:5.17.0
pie install --offline phalcon/cphalcon:5.17.0

or alternatively:

pie install --download-only phalcon/cphalcon:5.17.0
pie install --no-download phalcon/cphalcon:5.17.0

The second command should fail if any required artifact is missing from the local cache, rather than attempting network access.

I don't have a strong preference for the exact command-line interface; the important capability is separating "fetch" from "build/install".

What is actually happening

pie install always performs downloading and installation as a single operation, making it difficult to build extensions in environments where network access is intentionally restricted after dependencies have been fetched.

Complete logs/output

N/A

Anything else?

This would improve support for:

• reproducible builds
• hermetic/offline builds
• Docker BuildKit (RUN --network=none)
• CI environments with restricted or controlled egress
• build systems that separate dependency fetching from compilation

I believe this would make PIE fit well into modern container build workflows while also improving build reproducibility.