Phase 4: Migrate from Travis CI to GitHub Actions

Replaced deprecated Travis CI with modern GitHub Actions workflow
providing more comprehensive CI/CD coverage.

New GitHub Actions workflow features:
- Multi-OS testing: Ubuntu, macOS, Windows
- Multi-R version testing: release, devel, oldrel-1
- Automatic dependency installation with caching
- System dependency handling for spatial packages
- Code coverage reporting to Codecov
- Check results and test output artifacts on failure
- Warnings treated as errors for strict quality control

Travis CI limitations addressed:
- Travis CI is deprecated and no longer recommended
- Limited to single OS (Linux trusty)
- Manual dependency specification
- Less flexible matrix configuration

Updated README badge to show GitHub Actions status.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: dshkol

.github/workflows/R-CMD-check.yaml

@@ -0,0 +1,89 @@
+# GitHub Actions workflow for R CMD check
+# Replaces deprecated Travis CI configuration
+
+name: R-CMD-check
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+    branches: [main, master]
+
+jobs:
+  R-CMD-check:
+    runs-on: ${{ matrix.config.os }}
+
+    name: ${{ matrix.config.os }} (${{ matrix.config.r }})
+
+    strategy:
+      fail-fast: false
+      matrix:
+        config:
+          - {os: ubuntu-latest,   r: 'release'}
+          - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release'}
+          - {os: ubuntu-latest,   r: 'oldrel-1'}
+          - {os: macos-latest,    r: 'release'}
+          - {os: windows-latest,  r: 'release'}
+
+    env:
+      GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
+      R_KEEP_PKG_SOURCE: yes
+      PKG_CFLAGS: "-O3 -Wall -pedantic"
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: r-lib/actions/setup-pandoc@v2
+
+      - uses: r-lib/actions/setup-r@v2
+        with:
+          r-version: ${{ matrix.config.r }}
+          http-user-agent: ${{ matrix.config.http-user-agent }}
+          use-public-rspm: true
+
+      - name: Install system dependencies (Linux)
+        if: runner.os == 'Linux'
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y \
+            libudunits2-dev \
+            libproj-dev \
+            libgeos-dev \
+            libgdal-dev
+
+      - uses: r-lib/actions/setup-r-dependencies@v2
+        with:
+          extra-packages: |
+            any::rcmdcheck
+            any::covr
+          needs: check
+
+      - uses: r-lib/actions/check-r-package@v2
+        with:
+          upload-snapshots: true
+          error-on: 'warning'
+
+      - name: Show testthat output
+        if: always()
+        run: |
+          ## --------------------------------------------------------------------
+          find ${{ runner.temp }}/package -name 'testthat.Rout*' -exec cat '{}' \; || true
+        shell: bash
+
+      - name: Upload check results
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: ${{ runner.os }}-r${{ matrix.config.r }}-results
+          path: check
+
+      - name: Test coverage
+        if: success() && runner.os == 'Linux' && matrix.config.r == 'release'
+        run: |
+          Rscript -e 'covr::codecov(
+            quiet = FALSE,
+            clean = FALSE,
+            install_path = file.path(normalizePath(Sys.getenv("RUNNER_TEMP"), winslash = "/"), "package")
+          )'
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}

NEWS.md

@@ -1,5 +1,11 @@
 # `geohashTools` NEWS
 
+## v0.3.4 (Development)
+
+### INFRASTRUCTURE
+
+ 1. Migrated from deprecated Travis CI to GitHub Actions for continuous integration. New workflow tests across multiple R versions (release, devel, oldrel-1) and operating systems (Ubuntu, macOS, Windows), providing more comprehensive coverage. Badge updated in README.
+
 ## v0.3.3
 
 Drop references to deprecated rgdal.

README.md

@@ -8,8 +8,8 @@ output: github_document
 
 
 ![logo](logo.png "geohashTools")
+[![R-CMD-check](https://github.com/MichaelChirico/geohashTools/actions/workflows/R-CMD-check.yaml/badge.svg)](https://github.com/MichaelChirico/geohashTools/actions/workflows/R-CMD-check.yaml)
 [![codecov](https://codecov.io/gh/MichaelChirico/geohashTools/branch/master/graph/badge.svg)](https://app.codecov.io/gh/MichaelChirico/geohashTools?branch=master)
-[![Build Status](https://app.travis-ci.com/MichaelChirico/geohashTools.svg?branch=master)](https://app.travis-ci.com/MichaelChirico/geohashTools)
 [![CRAN status](https://www.r-pkg.org/badges/version/geohashTools)](https://cran.r-project.org/package=geohashTools)
 
 This package provides tools for working with [Gustavo](https://github.com/niemeyer) [Niemeyer](https://twitter.com/gniemeyer)'s [geohash](https://en.wikipedia.org/wiki/Geohash) system of nestable, compact global coordinates based on [Z-order curves](https://en.wikipedia.org/wiki/Z-order_curve). The system consists of carving the earth into equally-sized rectangles (when projected into latitude/longitude space) and nesting this process recursively.