Set bash to be default shell for Github Actions CI (#1037)

Shaves a few lines off the .github/workflows/*.yaml files.
See https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#defaultsrun.

Author: weiji14

.github/workflows/cache_data.yaml

@@ -12,6 +12,9 @@ jobs:
   gmt_cache:
     name: Cache GMT artifacts
     runs-on: macOS-latest
+    defaults:
+      run:
+        shell: bash -l {0}
 
     steps:
       # Setup Miniconda
@@ -23,21 +26,19 @@ jobs:
 
       # Install GMT
       - name: Install GMT
-        shell: bash -l {0}
         run: conda install -c conda-forge gmt=6.1.1
 
       # Download remote files
       - name: Download remote data
-        shell: bash -l {0}
         run: |
           gmt which -Ga @earth_relief_10m_p @earth_relief_10m_g \
                         @earth_relief_30m_p @earth_relief_30m_g \
                         @earth_relief_01d_p @earth_relief_01d_g \
                         @earth_relief_05m_p @earth_relief_05m_g
           # Download one tile of the 03s srtm data.
           # @N35E135.earth_relief_03s_g.nc is for internal use only.
-          # The naming scheme may change. 
-          # DO NOT USE IT IN SCRIPTS.         
+          # The naming scheme may change.
+          # DO NOT USE IT IN SCRIPTS.
           gmt which -Ga @N35E135.earth_relief_03s_g.nc
           gmt which -Ga @ridge.txt @Table_5_11.txt @test.dat.nc \
                         @tut_bathy.nc @tut_quakes.ngdc @tut_ship.xyz \

.github/workflows/ci_tests.yaml

@@ -45,6 +45,9 @@ jobs:
           - os: ubuntu-latest
             python-version: 3.8
             isDraft: true
+    defaults:
+      run:
+        shell: bash -l {0}
 
     # environmental variables used in coverage
     env:
@@ -76,12 +79,10 @@ jobs:
 
       # Install GMT and other required dependencies from conda-forge
       - name: Install dependencies
-        shell: bash -l {0}
         run: conda env update --file environment.yml
 
       # Show installed pkg information for postmortem diagnostic
       - name: List installed packages
-        shell: bash -l {0}
         run: conda list
 
       # Download cached remote files (artifacts) from GitHub
@@ -95,7 +96,6 @@ jobs:
 
       # Move downloaded files to ~/.gmt directory and list them
       - name: Move and list downloaded remote files
-        shell: bash -l {0}
         run: |
           mkdir -p ~/.gmt
           mv .gmt/* ~/.gmt
@@ -105,14 +105,12 @@ jobs:
 
       # Install the package that we want to test
       - name: Install the package
-        shell: bash -l {0}
         run: |
           python setup.py sdist --formats=zip
           pip install dist/*
 
       # Run the tests
       - name: Test with pytest
-        shell: bash -l {0}
         run: make test PYTEST_EXTRA="-r P"
 
       # Upload diff images on test failure
@@ -125,7 +123,6 @@ jobs:
 
       # Build the documentation
       - name: Build the documentation
-        shell: bash -l {0}
         run: make -C doc clean all
 
       # Upload coverage to Codecov

.github/workflows/ci_tests_dev.yaml

@@ -106,7 +106,6 @@ jobs:
 
       # Move downloaded files to ~/.gmt directory and list them
       - name: Move and list downloaded remote files
-        shell: bash -l {0}
         run: |
           mkdir -p ~/.gmt
           mv .gmt/* ~/.gmt