histedit: abort when attempting to fold subtree commits

Summary:
Currently, `histedit` does not combine the subtree metadata when it folds subtree commits,
so the subtree metadata can be lost. I’m not sure that simply merging the metadata would
fully solve the issue. Until we have a proper fix, this diff aborts `histedit` whenever a user
tries to fold subtree commits.

Reviewed By: muirdm

Differential Revision: D75897810

fbshipit-source-id: 3a29885d97a414afe646142ef82dd36299a4204a

Author: zzl0

eden/scm/sapling/ext/histedit.py

@@ -258,6 +258,7 @@
     visibility,
 )
 from sapling.i18n import _
+from sapling.utils import subtreeutil
 
 # pyre-fixme[11]: Annotation `pickle` is not defined as a type.
 pickle = util.pickle
@@ -1173,11 +1174,23 @@ def _histedit(ui, repo, state, *freeargs, **opts):
         # goal == goalnew
         _newhistedit(ui, repo, state, revs, freeargs, opts)
 
+    _abort_if_fold_subtree_commits(state)
     _continuehistedit(ui, repo, state)
     _finishhistedit(ui, repo, state, fm)
     fm.end()
 
 
+def _abort_if_fold_subtree_commits(state):
+    for action in state.actions:
+        if isinstance(action, fold):
+            extra = action.repo[action.node].extra()
+            if subtreeutil.get_subtree_metadata(extra):
+                raise error.Abort(
+                    _("histedit cannot fold/roll subtree commits"),
+                    hint=_("use '@prog@ fold' to combine subtree commits"),
+                )
+
+
 def _continuehistedit(ui, repo, state):
     """This function runs after either:
     - bootstrapcontinue (if the goal is 'continue')

eden/scm/tests/test-subtree-histedit.t

@@ -51,7 +51,19 @@ test histedit to fold subtree merge commits
   > pick 23b8d4a76647 merge B from foo to foo2
   > f c90acfc6d9e6 merge C from foo to foo3
   > EOF
-tofix: the combined commits should have two subtree merge metadata
+  abort: histedit cannot fold/roll subtree commits
+  (use 'hg fold' to combine subtree commits)
+  [255]
+  $ hg histedit 23b8d4a76647 --commands - <<EOF
+  > pick 23b8d4a76647 merge B from foo to foo2
+  > r c90acfc6d9e6 merge C from foo to foo3
+  > EOF
+  abort: histedit cannot fold/roll subtree commits
+  (use 'hg fold' to combine subtree commits)
+  [255]
+  $ hg fold --from 23b8d4a76647
+  2 changesets folded
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg subtree inspect -r .
   {
     "merges": [
@@ -60,6 +72,12 @@ tofix: the combined commits should have two subtree merge metadata
         "from_commit": "c4fbbcdf676b67867d7a51393f12109974c5da59",
         "from_path": "foo",
         "to_path": "foo2"
+      },
+      {
+        "version": 1,
+        "from_commit": "4701d37a062f216cc8ae6cebe85ce64a59cf6fc1",
+        "from_path": "foo",
+        "to_path": "foo3"
       }
     ]
   }