Add vcpkg support with megamimes overlay port

[Copilot]

The project previously only supported FetchContent for dependency management. This adds vcpkg manifest mode support, falling back to FetchContent when vcpkg is not detected.

Changes

vcpkg Detection (CMakeLists.txt, tests/CMakeLists.txt)

• Detects vcpkg by matching CMAKE_TOOLCHAIN_FILE against */scripts/buildsystems/vcpkg.cmake
• Sets VCPKG_TOOLCHAIN_ACTIVE and switches between find_package and FetchContent accordingly
• Target name differences handled per mode (unofficial::sqlite3::sqlite3 vs SQLite::SQLite3, megamimes::megamimes vs compiled-in source)

vcpkg Manifest (vcpkg.json, vcpkg-configuration.json)

• vcpkg.json declares dependencies: argparse, mio, sqlite3, megamimes
• vcpkg-configuration.json registers ./ports as the overlay ports directory so megamimes is resolved automatically

MegaMimes Overlay Port (ports/megamimes/)

MegaMimes has no native CMake build system and is absent from the vcpkg registry, so it is provided as an overlay port:

• portfile.cmake — fetches from kobbyowen/MegaMimes@b839068 (same commit as the existing FetchContent pin) with verified SHA512
• CMakeLists.txt — wrapper that builds a static library and exports the megamimes::megamimes target
• vcpkg.json — port manifest (MIT, version-date 2021-12-01)

Usage

cmake -B build \
  -DCMAKE_TOOLCHAIN_FILE=/path/to/vcpkg/scripts/buildsystems/vcpkg.cmake

With vcpkg active, all dependencies are resolved via find_package; without it, the original FetchContent path is unchanged.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/kobbyowen/MegaMimes/commits/b839068db99cbfcff1af8df1229bd7e41701fe96
  • Triggering command: /usr/bin/curl curl -s REDACTED (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Support vcpkg</issue_title>
<issue_description>I want this repo to support building using vcpkg the cmake system can detect if it's vcpkg using the following code:

# Check if CMAKE_TOOLCHAIN_FILE is set
if (DEFINED CMAKE_TOOLCHAIN_FILE)
    message(STATUS "CMAKE_TOOLCHAIN_FILE is set to: ${CMAKE_TOOLCHAIN_FILE}")

    # Check if the path points to the vcpkg toolchain file
    if ("${CMAKE_TOOLCHAIN_FILE}" MATCHES ".*[/\\\\]scripts[/\\\\]buildsystems[/\\\\]vcpkg.cmake$")
        message(STATUS "vcpkg toolchain file detected via path matching.")
        set(VCPKG_TOOLCHAIN_ACTIVE TRUE)
    endif()
endif()

And if it is not, proceed with old FetchContent approach. Otherwise, we should:

1. Build megamime as an overlay port
2. Find mio, argparse, sqlite, etc. using vcpkg.</issue_description>

<agent_instructions>No code changes should be necessary, this should only require a vcpkg.json and an overlay port.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Support vcpkg #37

---

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (3b25851) to head (037c179).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master       #38   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           60        60           
  Branches         4         4           
=========================================
  Hits            60        60           

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