feat: Add the option to specify external script files in addition to …

…inline scripts

README.md

@@ -121,6 +121,9 @@ Each entry in the `checks.scripts` array must specify the following settings:
 
 * `name`: an optional human-readable name for this check
 
+The parameters `run` and `file` are mutually exclusive, but at least one must be specified.
+The `shell` parameter is mandatory when using `run`.
+
 The custom script should use its exit code to indicate whether the updater should proceed
 (`exit code = 0`) or whether updates should be inhibited right now (any non-0 exit code).
 If `message` is not specified but the script has written text to `stdout`,
@@ -167,6 +170,11 @@ print("Python also works when installed")
 exit(1)
 """
 
+    [[checks.scripts]]
+        name = "Example external script"
+        # shell = "bash" # specifying a shell is optional for external scripts/programs
+        file = "/bin/true"
+
 [notify]
     dbus_notify = false         # Do not show notifications
 ```

src/ublue_update/update_inhibitors/custom.py

@@ -9,17 +9,22 @@
 
 
 def run_custom_check_script(script) -> dict:
-    if script.get('shell') != 'bash':
-        raise Exception('checks.scripts.*.shell must be set to \'bash\'')
+    if 'run' in script and 'shell' not in script:
+        raise Exception('checks.scripts.*: \'shell\' must be specified when \'run\' is used')
+
+    if 'run' in script and 'file' in script:
+        raise Exception('checks.scripts.*: Only one of \'run\' and \'file\' must be set for a given script')
 
     log.debug(f"Running script {script}")
 
-    # Run the specified custom script via bash
-    script_result = subprocess.run(
-        ['bash', '-c', script['run']],
-        capture_output=True,
-        check=False,
-    )
+    # Run the specified custom script
+    if 'run' in script:
+        run_args = [script['shell'], '-c', script['run']]
+    elif 'shell' in script:
+        run_args = [script['shell'], script['file']]
+    else:
+        run_args = [script['file']]
+    script_result = subprocess.run(run_args, capture_output=True, text=True, check=False)
 
     # An exit code of 0 means "OK", a non-zero exit code
     # means "Do not download or perform updates right now"