Merge pull request #208 from hartwork/issue-136-handle-dry-run-config…

…uration-attempt

Handle attempt to combine --dry-run with live configuration (fixes #136)

git_delete_merged_branches/_engine.py

@@ -53,6 +53,16 @@ def __init__(self, pattern):
         )
 
 
+class _CannotDryRunConfigurationError(_DmbException):
+    def __init__(self, force_reconfiguration):
+        message = (
+            "Arguments --configure and --dry-run are not compatible."
+            if force_reconfiguration
+            else f"{APP}' need for configuration and argument --dry-run are not compatible."
+        )
+        super().__init__(message)
+
+
 class DeleteMergedBranches:
     _CONFIG_KEY_CONFIGURED = "delete-merged-branches.configured"
     _CONFIG_VALUE_CONFIGURED = "5.0.0+"  # i.e. most ancient version with compatible config
@@ -159,6 +169,8 @@ def _is_configured(cls, git_config):
     def ensure_configured(self, force_reconfiguration):
         git_config = self._git.extract_git_config()
         if force_reconfiguration or not self._is_configured(git_config):
+            if self._git.pretend:
+                raise _CannotDryRunConfigurationError(force_reconfiguration)
             self._configure(git_config)
             git_config = self._git.extract_git_config()
         assert self._is_configured(git_config)

git_delete_merged_branches/_git.py

@@ -46,6 +46,10 @@ def __init__(self, messenger, pretend, verbose, work_dir=None):
         self._pretend = pretend
         self._working_directory = work_dir
 
+    @property
+    def pretend(self):
+        return self._pretend
+
     def _wrap_subprocess(self, subprocess_function, argv, is_write, pretend_result, env):
         pretend = is_write and self._pretend
         if self._verbose: