POC: Deduplicate the GMT cache download step into a composite action

.github/actions/download_gmt_cache/action.yml

@@ -0,0 +1,27 @@
+# Download the cached GMT remote data files
+#
+# GMT downloads remote data files (e.g. Earth relief grids) on demand. To avoid
+# hitting the data servers in every job, the files are cached once by the
+# 'cache_data.yaml' workflow and uploaded as the 'gmt-cache' artifact. This action
+# downloads that artifact into the ~/.gmt directory.
+#
+# The job must check out the repository before using this action, and needs the
+# 'actions: read' permission to download artifacts from other workflow runs.
+name: Download GMT cache
+description: Download the cached GMT remote data files into the ~/.gmt directory.
+
+runs:
+  using: composite
+  steps:
+    - name: Download remote data from GitHub
+      # The job default shell is not inherited by composite actions, so it's set here to
+      # match the login shell used by the workflows.
+      shell: bash -l {0}
+      run: |
+        # Download cached files to ~/.gmt directory and list them
+        gh run download --name gmt-cache --dir ~/.gmt/
+        # Change modification times of the two files, so GMT won't refresh it
+        touch ~/.gmt/gmt_data_server.txt ~/.gmt/gmt_hash_server.txt
+        ls -lhR ~/.gmt
+      env:
+        GH_TOKEN: ${{ github.token }}

.github/workflows/benchmarks.yml

@@ -69,14 +69,7 @@ jobs:
 
       # Download cached remote files (artifacts) from GitHub
       - name: Download remote data from GitHub
-        run: |
-          # Download cached files to ~/.gmt directory and list them
-          gh run download --name gmt-cache --dir ~/.gmt/
-          # Change modification times of the two files, so GMT won't refresh it
-          touch ~/.gmt/gmt_data_server.txt ~/.gmt/gmt_hash_server.txt
-          ls -lhR ~/.gmt
-        env:
-          GH_TOKEN: ${{ github.token }}
+        uses: ./.github/actions/download_gmt_cache
 
       # Install the package that we want to test
       - name: Install the package

.github/workflows/ci_docs.yml

@@ -123,14 +123,7 @@ jobs:
 
       # Download cached remote files (artifacts) from GitHub
       - name: Download remote data from GitHub
-        run: |
-          # Download cached files to ~/.gmt directory and list them
-          gh run download --name gmt-cache --dir ~/.gmt/
-          # Change modification times of the two files, so GMT won't refresh it
-          touch ~/.gmt/gmt_data_server.txt ~/.gmt/gmt_hash_server.txt
-          ls -lhR ~/.gmt
-        env:
-          GH_TOKEN: ${{ github.token }}
+        uses: ./.github/actions/download_gmt_cache
 
       # Install the package that we want to test
       - name: Install the package

.github/workflows/ci_doctests.yaml

@@ -69,14 +69,7 @@ jobs:
 
       # Download cached remote files (artifacts) from GitHub
       - name: Download remote data from GitHub
-        run: |
-          # Download cached files to ~/.gmt directory and list them
-          gh run download --name gmt-cache --dir ~/.gmt/
-          # Change modification times of the two files, so GMT won't refresh it
-          touch ~/.gmt/gmt_data_server.txt ~/.gmt/gmt_hash_server.txt
-          ls -lhR ~/.gmt
-        env:
-          GH_TOKEN: ${{ github.token }}
+        uses: ./.github/actions/download_gmt_cache
 
       # Install the package that we want to test
       - name: Install the package

.github/workflows/ci_tests.yaml

@@ -145,14 +145,7 @@ jobs:
 
       # Download cached remote files (artifacts) from GitHub
       - name: Download remote data from GitHub
-        run: |
-          # Download files to ~/.gmt directory and list them
-          gh run download --name gmt-cache --dir ~/.gmt/
-          # Change modification times of the two files, so GMT won't refresh it
-          touch ~/.gmt/gmt_data_server.txt ~/.gmt/gmt_hash_server.txt
-          ls -lhR ~/.gmt
-        env:
-          GH_TOKEN: ${{ github.token }}
+        uses: ./.github/actions/download_gmt_cache
 
       # Install the package that we want to test
       - name: Install the package

.github/workflows/ci_tests_dev.yaml

@@ -151,14 +151,7 @@ jobs:
 
       # Download cached remote files (artifacts) from GitHub
       - name: Download remote data from GitHub
-        run: |
-          # Download cached files to ~/.gmt directory and list them
-          gh run download --name gmt-cache --dir ~/.gmt/
-          # Change modification times of the two files, so GMT won't refresh it
-          touch ~/.gmt/gmt_data_server.txt ~/.gmt/gmt_hash_server.txt
-          ls -lhR ~/.gmt
-        env:
-          GH_TOKEN: ${{ github.token }}
+        uses: ./.github/actions/download_gmt_cache
 
       # Install the package that we want to test
       - name: Install the package

.github/workflows/ci_tests_legacy.yaml

@@ -80,14 +80,7 @@ jobs:
 
       # Download cached remote files (artifacts) from GitHub
       - name: Download remote data from GitHub
-        run: |
-          # Download cached files to ~/.gmt directory and list them
-          gh run download --name gmt-cache --dir ~/.gmt/
-          # Change modification times of the two files, so GMT won't refresh it.
-          touch ~/.gmt/gmt_data_server.txt ~/.gmt/gmt_hash_server.txt
-          ls -lhR ~/.gmt
-        env:
-          GH_TOKEN: ${{ github.token }}
+        uses: ./.github/actions/download_gmt_cache
 
       # Install the package that we want to test
       - name: Install the package