[CI] Run regression tests for different parallelizations in parallel

.github/workflows/appimage.yml

@@ -33,6 +33,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
+        parallelization: [0, 1, 2]
 
     steps:
     - uses: actions/download-artifact@v3
@@ -66,5 +67,12 @@ jobs:
 
     - name: Regression Tests
       run: |
-        export RATARMOUNT_CMD=/usr/local/bin/ratarmount
+        # Starting up ratarmount for each very short test is quite slow, especially on the CI machine (3-5s).
+        # On my local machine, it's around 1s, which is not good, but also not bad.
+        # The AppImage extraction script is already tested in the simple tests above, so it should be fine
+        # to extract it once and then test the AppRun script, which still modifies the LD_LIBRARY_PATH and
+        # still uses the bundled libaries, i.e., it still is a good integrity test for the AppImage.
+        /usr/local/bin/ratarmount --appimage-extract
+        export RATARMOUNT_CMD=$PWD/squashfs-root/AppRun
+        export PARALLELIZATIONS=${{ matrix.parallelization }}
         bash tests/runtests.sh

AppImage/build-ratarmount-appimage.sh

@@ -246,7 +246,8 @@ trimAppImage
 
 echo "Create AppImage from Modified AppDir"
 # times and sizes for ratarmount.AppImage --help on T14: --comp gzip: 1.6s, 12.50 MB, --comp xz: 3.0s, 12.88 MB
-APPIMAGE_EXTRACT_AND_RUN=1 ARCH="$APPIMAGE_ARCH" appimagetool --comp gzip --no-appstream "$APP_BASE".App{Dir,Image}
+# times and sizes for ratarmount.AppImage --help on Ryzen 3900X: --comp gzip: 1.2s, 15.09 MB, --comp xz: 2.2s, 14.59 MB
+APPIMAGE_EXTRACT_AND_RUN=1 ARCH="$APPIMAGE_ARCH" appimagetool --comp xz --no-appstream "$APP_BASE".App{Dir,Image}
 
 chmod u+x "$APP_BASE.AppImage"
 version=$( ./"$APP_BASE.AppImage" --version | sed -n -E 's|ratarmount ([0-9.]+)|\1|p' &>/dev/null )

tests/runtests.sh

@@ -13,6 +13,9 @@ RATARMOUNT_CMD="$RATARMOUNT_CMD --index-minimum-file-count 0"
 export RATARMOUNT_CMD
 echo "RATARMOUNT_CMD: $RATARMOUNT_CMD"
 
+if [[ -z "$PARALLELIZATIONS" ]]; then
+    PARALLELIZATIONS="1 2 0"
+fi
 
 # MAC does not have mountpoint check!
 if ! command -v mountpoint &>/dev/null; then
@@ -1890,7 +1893,7 @@ pytestedTests+=(
 )
 
 
-for parallelization in 1 2 0; do
+for parallelization in $PARALLELIZATIONS; do
 
 echo "== Testing with -P $parallelization =="
 export parallelization