Add soft reset functionality for workspaces

Add `--soft` option to `bst workspace reset` which would allow uses to
reset workspace-related state without affecting its contents. This will
be useful in case when an user wants to re-run configure-commands for a
workspaced element.

Patch originally by Chandan Singh, rebased against recent refactor.

Fixes #375.

2 files changed, 13 insertions, 4 deletions

diff --git a/buildstream/_frontend/cli.py b/buildstream/_frontend/cli.py
index 41736ac2f..230c8427a 100644
--- a/buildstream/_frontend/cli.py
+++ b/buildstream/_frontend/cli.py
@@ -651,6 +651,8 @@ def workspace_close(app, remove_dir, all_, elements):
 #                     Workspace Reset Command                    #
 ##################################################################
 @workspace.command(name='reset', short_help="Reset a workspace to its original state")
+@click.option('--soft', default=False, is_flag=True,
+              help="Reset workspace state without affecting its contents")
 @click.option('--track', 'track_', default=False, is_flag=True,
               help="Track and fetch the latest source before resetting")
 @click.option('--all', '-a', 'all_', default=False, is_flag=True,
@@ -658,7 +660,7 @@ def workspace_close(app, remove_dir, all_, elements):
 @click.argument('elements', nargs=-1,
                 type=click.Path(dir_okay=False, readable=True))
 @click.pass_obj
-def workspace_reset(app, track_, all_, elements):
+def workspace_reset(app, soft, track_, all_, elements):
     """Reset a workspace to its original state"""
 
     # Check that the workspaces in question exist
@@ -677,7 +679,7 @@ def workspace_reset(app, track_, all_, elements):
         if nonexisting:
             raise AppError("Workspace does not exist", detail="\n".join(nonexisting))
 
-        if app.interactive:
+        if app.interactive and not soft:
             if not click.confirm('This will remove all your changes, are you sure?'):
                 click.echo('Aborting', err=True)
                 sys.exit(-1)
@@ -685,7 +687,7 @@ def workspace_reset(app, track_, all_, elements):
         if all_:
             elements = tuple(element_name for element_name, _ in app.project.workspaces.list())
 
-        app.stream.workspace_reset(elements, track_first=track_)
+        app.stream.workspace_reset(elements, soft=soft, track_first=track_)
 
 
 ##################################################################
diff --git a/buildstream/_stream.py b/buildstream/_stream.py
index c8d0bb69c..a5eacacf0 100644
--- a/buildstream/_stream.py
+++ b/buildstream/_stream.py
@@ -504,9 +504,10 @@ class Stream():
     #
     # Args:
     #    targets (list of str): The target elements to reset the workspace for
+    #    soft (bool): Only reset workspace state
     #    track_first (bool): Whether to also track the sources first
     #
-    def workspace_reset(self, targets, *, track_first):
+    def workspace_reset(self, targets, *, soft, track_first):
 
         if track_first:
             track_targets = targets
@@ -522,6 +523,12 @@ class Stream():
         for element in elements:
             workspace = self._project.workspaces.get_workspace(element.name)
 
+            if soft:
+                workspace.prepared = False
+                self._message(MessageType.INFO, "Reset workspace state for {} at: {}"
+                              .format(element.name, workspace.path))
+                continue
+
             with element.timed_activity("Removing workspace directory {}"
                                         .format(workspace.path)):
                 try: