sidedata: apply basic but tight security around exchange

We don't currently have code to deal with exchange between repository using
sidedata and repository not using sidedata. Until we implement such code (eg:
dropping side data when pushing to a non-sidedata repo) we prevent the two kind
of repo to speak to each other. This is somewhere similar to what 'treemanifest'
does.

Note that sidedata exchange is broken unless one use changegroup v3 anyway. See
next changeset for details.

Differential Revision: https://phab.mercurial-scm.org/D6939

mercurial/bundle2.py

@@ -1711,6 +1711,8 b' def _addpartsfromopts(ui, repo, bundler,'
             part.addparam(
                 b'targetphase', b'%d' % phases.secret, mandatory=False
             )
+        if b'exp-sidedata-flag' in repo.requirements:
+            part.addparam(b'exp-sidedata', b'1')
 
     if opts.get(b'streamv2', False):
         addpartbundlestream2(bundler, repo, stream=True)
@@ -1930,7 +1932,14 b' def combinechangegroupresults(op):'
 
 
 @parthandler(
-    b'changegroup', (b'version', b'nbchanges', b'treemanifest', b'targetphase')
+    b'changegroup',
+    (
+        b'version',
+        b'nbchanges',
+        b'exp-sidedata',
+        b'treemanifest',
+        b'targetphase',
+    ),
 )
 def handlechangegroup(op, inpart):
     """apply a changegroup part on the repo
@@ -1965,6 +1974,14 b' def handlechangegroup(op, inpart):'
             op.repo.ui, op.repo.requirements, op.repo.features
         )
         op.repo._writerequirements()
+
+    bundlesidedata = bool(b'exp-sidedata' in inpart.params)
+    reposidedata = bool(b'exp-sidedata-flag' in op.repo.requirements)
+    if reposidedata and not bundlesidedata:
+        msg = b"repository is using sidedata but the bundle source do not"
+        hint = b'this is currently unsupported'
+        raise error.Abort(msg, hint=hint)
+
     extrakwargs = {}
     targetphase = inpart.params.get(b'targetphase')
     if targetphase is not None:
@@ -2551,5 +2568,7 b' def widen_bundle('
         part.addparam(b'version', cgversion)
         if b'treemanifest' in repo.requirements:
             part.addparam(b'treemanifest', b'1')
+        if b'exp-sidedata-flag' in repo.requirements:
+            part.addparam(b'exp-sidedata', b'1')
 
     return bundler

mercurial/exchange.py

@@ -1049,6 +1049,8 b' def _pushb2ctx(pushop, bundler):'
         cgpart.addparam(b'version', version)
     if b'treemanifest' in pushop.repo.requirements:
         cgpart.addparam(b'treemanifest', b'1')
+    if b'exp-sidedata-flag' in pushop.repo.requirements:
+        cgpart.addparam(b'exp-sidedata', b'1')
 
     def handlereply(op):
         """extract addchangegroup returns from server reply"""
@@ -2511,6 +2513,9 b' def _getbundlechangegrouppart('
     if b'treemanifest' in repo.requirements:
         part.addparam(b'treemanifest', b'1')
 
+    if b'exp-sidedata-flag' in repo.requirements:
+        part.addparam(b'exp-sidedata', b'1')
+
     if (
         kwargs.get(r'narrow', False)
         and kwargs.get(r'narrow_acl', False)