Patchwork D9680: sharesafe: add functionality to automatically downgrade shares

diff --git a/tests/test-share-safe.t b/tests/test-share-safe.t
--- a/tests/test-share-safe.t
+++ b/tests/test-share-safe.t
@@ -484,6 +484,20 @@ 
   abort: share source does not support exp-sharesafe requirement
   [255]
 
+Testing automatic downgrade of shares when config is set
+  $ hg log -GT "{node}: {desc}\n" -R ../ss-share --config experimental.sharesafe-auto-downgrade-shares=true
+  repository downgraded to not use share-safe mode
+  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
+  |
+  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
+  
+
+  $ hg log -GT "{node}: {desc}\n" -R ../ss-share
+  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
+  |
+  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
+  
+
 
 Testing automatic upgrade of shares when config is set
 
diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -1613,6 +1613,23 @@ 
     return current_requirements
 
 
+def downgrade_share_to_non_safe(
+    hgvfs, current_requirements, source_requirements
+):
+    """Downgrades a share which use share-safe to not use it
+
+    Returns the set of new repository requirements
+    """
+    # we cannot be 100% sure on which requirements were present in store when
+    # the source supported share-safe. However, we do know that working
+    # directory requirements were not there. Hence we remove them
+    source_requirements -= requirementsmod.WORKING_DIR_REQUIREMENTS
+    current_requirements |= source_requirements
+    current_requirements.remove(requirementsmod.SHARESAFE_REQUIREMENT)
+    writerequires(hgvfs, current_requirements)
+    return current_requirements
+
+
 class filecachesubentry(object):
     def __init__(self, path, stat):
         self.path = path
diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -574,11 +574,24 @@ 
             and requirementsmod.SHARESAFE_REQUIREMENT
             not in _readrequires(sharedvfs, True)
         ):
-            raise error.Abort(
-                _(b"share source does not support exp-sharesafe requirement")
-            )
-
-        requirements |= _readrequires(storevfs, False)
+            if ui.configbool(
+                b'experimental', b'sharesafe-auto-downgrade-shares'
+            ):
+                sourcerequires = _readrequires(sharedvfs, True)
+                requirements = scmutil.downgrade_share_to_non_safe(
+                    hgvfs, requirements, sourcerequires
+                )
+                ui.warn(
+                    _(b'repository downgraded to not use share-safe mode\n')
+                )
+            else:
+                raise error.Abort(
+                    _(
+                        b"share source does not support exp-sharesafe requirement"
+                    )
+                )
+        else:
+            requirements |= _readrequires(storevfs, False)
     elif shared:
         sourcerequires = _readrequires(sharedvfs, False)
         if requirementsmod.SHARESAFE_REQUIREMENT in sourcerequires:
diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -1074,6 +1074,11 @@ 
 )
 coreconfigitem(
     b'experimental',
+    b'sharesafe-auto-downgrade-shares',
+    default=False,
+)
+coreconfigitem(
+    b'experimental',
     b'sharesafe-auto-upgrade-shares',
     default=False,
 )