diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -44,6 +44,7 @@
     hbisect,
     help,
     hg,
+    localrepo,
     logcmdutil,
     merge as mergemod,
     mergestate as mergestatemod,
@@ -66,6 +67,7 @@
     ui as uimod,
     util,
     verify as verifymod,
+    vfs as vfsmod,
     wireprotoserver,
 )
 from .utils import (
@@ -2141,6 +2143,7 @@
         (b'u', b'untrusted', None, _(b'show untrusted configuration options')),
         (b'e', b'edit', None, _(b'edit user config')),
         (b'l', b'local', None, _(b'edit repository config')),
+        (b'', b'share', None, _(b'edit share source config (EXPERIMENTAL)')),
         (b'g', b'global', None, _(b'edit global config')),
     ]
     + formatteropts,
@@ -2179,22 +2182,34 @@
       :source:  String. Filename and line number where the item is defined.
       :value:   String. Config value.
 
+      The --share flag can be used to edit the config file of share source
+      repository. It only works when you have shared using the experimental safe
+      method.
+
     Returns 0 on success, 1 if NAME does not exist.
 
     """
 
     opts = pycompat.byteskwargs(opts)
-    editopts = (b'edit', b'local', b'global')
+    editopts = (b'edit', b'local', b'global', b'share')
     if any(opts.get(o) for o in editopts):
-        if opts.get(b'local') and opts.get(b'global'):
-            raise error.Abort(_(b"can't use --local and --global together"))
-
+        cmdutil.check_at_most_one_arg(opts, *editopts[1:])
         if opts.get(b'local'):
             if not repo:
                 raise error.Abort(_(b"can't use --local outside a repository"))
             paths = [repo.vfs.join(b'hgrc')]
         elif opts.get(b'global'):
             paths = rcutil.systemrcpath()
+        elif opts.get(b'share'):
+            if not repo.shared():
+                raise error.Abort(
+                    _(b"repository is not shared one, can't use --share")
+                )
+                if localrepo.SHARESAFE_REQUIREMENT not in repo.requirements:
+                    raise error.Abort(
+                        _(b"this does not support editing share source config")
+                    )
+            paths = [vfsmod.vfs(repo.sharedpath).join(b'hgrc')]
         else:
             paths = rcutil.userrcpath()
 
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
@@ -33,6 +33,10 @@
   $ hg ci -Aqm "added a"
   $ echo b > b
   $ hg ci -Aqm "added b"
+
+  $ HGEDITOR=cat hg config --share
+  abort: repository is not shared one, can't use --share
+  [255]
   $ cd ..
 
 Create a shared repo and check the requirements are shared and read correctly
@@ -85,6 +89,14 @@
   $ hg showconfig ui.curses
   false
 
+  $ HGEDITOR=cat hg config --share
+  [ui]
+  curses=true
+
+  $ HGEDITOR=cat hg config --local
+  [ui]
+  curses=false
+
 Testing that hooks set in source repository also runs in shared repo
 
   $ cd ../source