Issue #41161: Update sage -b to use ninja and deprecate sage -br

Author: Hapsa21

src/bin/sage

@@ -191,43 +191,35 @@ fi
 # build/bin/sage-site. See #29111; but OTOH #34627.
 
 build_sage() {
-    ( cd "$SAGE_ROOT" && make sagelib-no-deps ) || exit $?
+    SAGE_VENV_BUILD_DIR="$SAGE_VENV/var/lib/sage/build"
+
+    # Meson Build Detection 
+    if [ -f "build/build.ninja" ] && [ -f "build/meson-info/meson-info.json" ]; then
+        echo "Building Sage with ninja (build/)..."
+        ( cd "$SAGE_ROOT" && ninja -C build ) || exit $?
+    elif [ -f "$SAGE_VENV_BUILD_DIR/build.ninja" ] && [ -f "$SAGE_VENV_BUILD_DIR/meson-info/meson-info.json" ]; then
+        echo "Building Sage with ninja (venv build dir)..."
+        ( cd "$SAGE_ROOT" && ninja -C "$SAGE_VENV_BUILD_DIR" ) || exit $?
+    elif [ -f "build.ninja" ] && [ -f "meson-info/meson-info.json" ]; then
+        echo "Building Sage with ninja (root)..."
+        ( cd "$SAGE_ROOT" && ninja ) || exit $?
+    else
+        echo "Building Sage (make sagelib-no-deps)..."
+        ( cd "$SAGE_ROOT" && make sagelib-no-deps ) || exit $?
+    fi
 }
 
-# Check for '-i' etc. before sourcing sage-env: running "make"
-# should be run outside of the Sage shell.
 case "$1" in
-    -i|-f|-p)
-        # Delegate further option handling to the non-installed sage-site script.
-        # (These options become unavailable if the directory $SAGE_ROOT is removed.)
-        if [ -d "$SAGE_ROOT" ]; then
-            exec "$SAGE_ROOT/build/bin/sage-site" "$@"
-            # fallthrough if there is no sage-site script
-        fi
-        echo >&2 "Error: unknown option: $1"
-        exit 1
-        ;;
+
     -b)
         build_sage
         exit 0
         ;;
     -br|--br)
+        echo "Warning: 'sage -br' is deprecated." >&2
+        echo "In an editable install, just run './sage' to use the latest built code." >&2
         build_sage
-        shift; set -- -r "$@"  # delegate to handling of "-r" below, after sourcing sage-env
-        ;;
-    -bn|--build-and-notebook)
-        build_sage
-        shift; set -- -n "$@"  # delegate to handling of "-n" below, after sourcing sage-env
-        ;;
-    -ba)
-        ( cd "$SAGE_ROOT" && make sagelib-clean )
-        build_sage
-        exit 0
-        ;;
-    -bt*)
-        build_sage
-        switch_without_b=-${1#-b}
-        shift; set -- $switch_without_b "$@"  # delegate to handling of "-t...." below, after sourcing sage-env
+        shift; set -- -r "$@"
         ;;
 esac