Handle passwordless sudo in install script

scripts/install.sh

@@ -131,15 +131,15 @@ checkConflictingInstallation() {
     fi
 }
 
-# Install the binary and ask for elevated permissions if needed
+# Install the binary, using sudo if the directory is not directly writable
 installBinary() {
-    if [ "$INSTALL_DIR" = "/usr/local/bin" ]; then
+    if { [ -d "$INSTALL_DIR" ] && [ -w "$INSTALL_DIR" ]; } || { [ ! -d "$INSTALL_DIR" ] && [ -w "$(dirname "$INSTALL_DIR")" ]; }; then
+        install -d "$INSTALL_DIR"
+        install rill "$INSTALL_DIR"
+    else
         printf "\nElevated permissions required to install the Rill binary to: %s/rill\n" "$INSTALL_DIR"
         sudo install -d "$INSTALL_DIR"
         sudo install rill "$INSTALL_DIR"
-    else
-        install -d "$INSTALL_DIR"
-        install rill "$INSTALL_DIR"
     fi
     cd - > /dev/null
 }
@@ -225,13 +225,18 @@ removePathConfigEntries() {
     done
 }
 
-# Check if the install directory (or its parent, if it doesn't exist yet) is writable
+# Check if we can install to INSTALL_DIR
 installDirIsWritable() {
-    if [ -d "$INSTALL_DIR" ]; then
-        [ -w "$INSTALL_DIR" ]
-    else
-        [ -w "$(dirname "$INSTALL_DIR")" ]
+    # Check if it is directly writable
+    if [ -d "$INSTALL_DIR" ] && [ -w "$INSTALL_DIR" ]; then
+        return 0
+    # If it doesn't exist yet, check if the parent directory is writable
+    elif [ ! -d "$INSTALL_DIR" ] && [ -w "$(dirname "$INSTALL_DIR")" ]; then
+        return 0
     fi
+
+    # Lastly, we also consider it writable if we have passwordless sudo (since then we don't need to prompt/error due to lack of permissions)
+    sudo -n true 2>/dev/null
 }
 
 # Resolve the install directory
@@ -248,18 +253,20 @@ resolveInstallDir() {
 
     # Handle non-interactive scenarios where prompt or sudo are not possible
     if [ "$NON_INTERACTIVE" = "true" ]; then
-        # If the install directory was explicitly set and requires sudo, we error
-        if [ -n "$INSTALL_DIR" ] && [ "$INSTALL_DIR_EXPLICIT" = "true" ] && ! installDirIsWritable; then
-            printf "Install directory '%s' requires elevated permissions, which are not available in non-interactive mode.\n" "$INSTALL_DIR"
-            exit 1
+        # Default to /usr/local/bin if not set.
+        if [ -z "$INSTALL_DIR" ]; then
+            INSTALL_DIR="/usr/local/bin"
         fi
 
-        # If the install directory is not set, or the previous installation path requires sudo, we default to installing in the current directory
-        if [ -z "$INSTALL_DIR" ]; then
-            printf "Non-interactive shell detected; defaulting to install in current directory.\n"
-            INSTALL_DIR=$(pwd)
-        elif ! installDirIsWritable; then
-            printf "Non-interactive shell detected; previous installation at '%s' requires elevated permissions; defaulting to install in current directory.\n" "$INSTALL_DIR"
+        # Handle if the install directory is not writable and we can't prompt due to non-interactive mode.
+        if ! installDirIsWritable; then
+            # Error if the install directory was set explicitly.
+            if [ "$INSTALL_DIR_EXPLICIT" = "true" ]; then
+                printf "Install directory '%s' requires elevated permissions, which are not available in non-interactive mode.\n" "$INSTALL_DIR"
+                exit 1
+            fi
+
+            # Fall back to the current directory otherwise (which we assume is writable).
             INSTALL_DIR=$(pwd)
         fi