diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -69,6 +69,7 @@
     pycompat,
     registrar,
     repair,
+    requirements as requirementsmod,
     revlog,
     revset,
     revsetlang,
@@ -3695,6 +3696,107 @@
 
 
 @command(
+    b'debugsharesafe',
+    [
+        (b'', b'upgrade', False, _(b'upgrade current share to share safe')),
+        (b'', b'downgrade', False, _(b'downgrade current share')),
+        (b'', b'force', False, _(b'forcefully perform operation')),
+    ],
+)
+def debugsharesafe(ui, repo, *args, **opts):
+    """upgrade or downgrade shares to enable/disable share-safe mode"""
+    if not repo.shared():
+        raise error.InputError(_(b"current repository is not shared one"))
+
+    cmdutil.check_at_most_one_arg(opts, 'upgrade', 'downgrade')
+    upgrade = opts.get('upgrade')
+    downgrade = opts.get('downgrade')
+
+    if not upgrade and not downgrade:
+        raise error.InputError(_(b"nothing specified"))
+
+    current_requirements = repo.requirements
+    if upgrade:
+        if requirementsmod.SHARESAFE_REQUIREMENT in current_requirements:
+            raise error.StateError(
+                _(b"repository already uses share-safe method")
+            )
+
+        sharesourcerequires = localrepo._readrequires(
+            localrepo._getsharedvfs(repo.vfs, current_requirements), False
+        )
+        if requirementsmod.SHARESAFE_REQUIREMENT not in sharesourcerequires:
+            raise error.StateError(
+                _(
+                    b"share source does not support share-safe, unable to upgrade"
+                )
+            )
+
+        # share source has SHARESAFE requirement present, hence all the
+        # requirements will be store requires
+        storerequires = localrepo._readrequires(repo.svfs, False)
+
+        # after upgrade, store requires will be shared, so lets find
+        # the requirements which are not present in store and
+        # write them to share's .hg/requires
+        diffrequires = current_requirements - storerequires
+        # add share-safe requirement as it will mark the share as share-safe
+        diffrequires.add(requirementsmod.SHARESAFE_REQUIREMENT)
+        scmutil.writerequires(repo.vfs, diffrequires)
+        ui.status(_(b"repository upgraded to use share-safe functionality\n"))
+        ui.status(
+            _(
+                b"requirements and configs of shared-source will be "
+                b"read from now onwards\n"
+            )
+        )
+    else:
+        if requirementsmod.SHARESAFE_REQUIREMENT not in current_requirements:
+            raise error.StateError(
+                _(b"repository does not uses share safe method, nothing to do")
+            )
+
+        sharesourcerequires = localrepo._readrequires(
+            localrepo._getsharedvfs(repo.vfs, current_requirements), False
+        )
+
+        if requirementsmod.SHARESAFE_REQUIREMENT in sharesourcerequires:
+            # we should copy the store requires in .hg/requires and remove
+            # share-safe requirement
+            storerequires = localrepo._readrequires(repo.svfs, False)
+            current_requirements |= storerequires
+            current_requirements.remove(requirementsmod.SHARESAFE_REQUIREMENT)
+            scmutil.writerequires(repo.vfs, current_requirements)
+            ui.status(
+                _(
+                    b"repository downgraded to not use share-safe functionality\n"
+                )
+            )
+        else:
+            # share source does not use share-safe and has requirements in
+            # .hg/requires. We cannot be sure which requirement were shared
+            # earlier in share-safe mode. In other words, there can be wdir
+            # specific requirements which should not be copied but we have
+            # no way to detect them
+            if not opts.get('force'):
+                raise error.Abort(
+                    _(
+                        b"shared source does not support share-safe "
+                        b"functionality, downgrading may not lead correct result"
+                    ),
+                    hint=_(b"use --force to still downgrade"),
+                )
+            current_requirements |= sharesourcerequires
+            current_requirements.remove(requirementsmod.SHARESAFE_REQUIREMENT)
+            scmutil.writerequires(repo.vfs, current_requirements)
+            ui.status(
+                _(
+                    b"repository downgraded to not use share-safe functionality\n"
+                )
+            )
+
+
+@command(
     b'debugsub',
     [(b'r', b'rev', b'', _(b'revision to check'), _(b'REV'))],
     _(b'[-r REV] [REV]'),
diff --git a/tests/test-completion.t b/tests/test-completion.t
--- a/tests/test-completion.t
+++ b/tests/test-completion.t
@@ -129,6 +129,7 @@
   debugrevspec
   debugserve
   debugsetparents
+  debugsharesafe
   debugsidedata
   debugssl
   debugstrip
@@ -318,6 +319,7 @@
   debugrevspec: optimize, show-revs, show-set, show-stage, no-optimized, verify-optimized
   debugserve: sshstdio, logiofd, logiofile
   debugsetparents: 
+  debugsharesafe: upgrade, downgrade, force
   debugsidedata: changelog, manifest, dir
   debugssl: 
   debugstrip: rev, force, no-backup, nobackup, , keep, bookmark, soft
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -1068,6 +1068,8 @@
    debugserve    run a server with advanced settings
    debugsetparents
                  manually set the parents of the current working directory
+   debugsharesafe
+                 upgrade or downgrade shares to enable/disable share-safe mode
    debugsidedata
                  dump the side data for a cl/manifest/file revision
    debugssl      test a secure connection to a server
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
@@ -70,6 +70,16 @@
   $ echo c > c
   $ hg ci -Aqm "added c"
 
+  $ hg debugsharesafe
+  abort: nothing specified
+  [10]
+  $ hg debugsharesafe --upgrade --downgrade
+  abort: cannot specify both --upgrade and --downgrade
+  [10]
+  $ hg debugsharesafe --upgrade
+  abort: repository already uses share-safe method
+  [20]
+
 Check that config of the source repository is also loaded
 
   $ hg showconfig ui.curses
@@ -399,6 +409,26 @@
   o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
   
 
+  $ hg debugsharesafe -R ../nss-share --downgrade
+  warning: source repository supports share-safe functionality. Reshare to upgrade.
+  abort: repository does not uses share safe method, nothing to do
+  [20]
+
+  $ hg debugsharesafe -R ../nss-share --upgrade
+  warning: source repository supports share-safe functionality. Reshare to upgrade.
+  repository upgraded to use share-safe functionality
+  requirements and configs of shared-source will be read from now onwards
+
+  $ hg log -GT "{node}: {desc}\n" -R ../nss-share
+  @  f63db81e6dde1d9c78814167f77fb1fb49283f4f: added bar
+  |
+  o  f3ba8b99bb6f897c87bbc1c07b75c6ddf43a4f77: added foo
+  
+
+  $ hg debugsharesafe -R ../nss-share --downgrade
+  repository downgraded to not use share-safe functionality
+
+
 
 Create a safe share from upgrade one