Run Cygwin CI workflow commands in login shells

.github/workflows/cygwin-test.yml

@@ -10,30 +10,36 @@ jobs:
       fail-fast: false
 
     env:
-      CHERE_INVOKING: 1
-      TMP: "/tmp"
-      TEMP: "/tmp"
+      CHERE_INVOKING: "1"
+      CYGWIN_NOWINPATH: "1"
 
     defaults:
       run:
-        shell: C:\cygwin\bin\bash.exe --noprofile --norc -exo pipefail -o igncr "{0}"
+        shell: C:\cygwin\bin\bash.exe --login --norc -eo pipefail -o igncr "{0}"
 
     steps:
     - name: Force LF line endings
       run: |
         git config --global core.autocrlf false  # Affects the non-Cygwin git.
-      shell: bash
+      shell: bash  # Use Git Bash instead of Cygwin Bash for this step.
 
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
         submodules: recursive
 
-    - uses: cygwin/cygwin-install-action@v4
+    - name: Install Cygwin
+      uses: cygwin/cygwin-install-action@v4
       with:
         packages: python39 python39-pip python39-virtualenv git
+        add-to-path: false  # No need to change $PATH outside the Cygwin environment.
 
-    - name: Special configuration for Cygwin's git
+    - name: Arrange for verbose output
+      run: |
+        # Arrange for verbose output but without shell environment setup details.
+        echo 'set -x' >~/.bash_profile
+
+    - name: Special configuration for Cygwin git
       run: |
         git config --global --add safe.directory "$(pwd)"
         git config --global core.autocrlf false
@@ -57,7 +63,7 @@ jobs:
 
     - name: Install project and test dependencies
       run: |
-        python -m pip install ".[test]"
+        pip install ".[test]"
 
     - name: Show version and platform information
       run: |
@@ -71,4 +77,4 @@ jobs:
 
     - name: Test with pytest
       run: |
-        python -m pytest --color=yes -p no:sugar --instafail -vv
+        pytest --color=yes -p no:sugar --instafail -vv