bundle2: don't advertise stream bundle2 capability when feature disabled

The server.uncompressed config option can be used to disable streaming
clones. While the top-level capability to advertise streaming clone
support isn't advertised when this option is set, we were still sending
the bundle2-level capabilities advertising support for stream parts.
It makes sense to not advertise that support when streaming clones
are globally disabled.

If the structure of the new code seems a bit odd, it is because we'll
have to further tweak the behavior in commit(s) ahead.

Differential Revision: https://phab.mercurial-scm.org/D1929

mercurial/bundle2.py

@@ -1519,8 +1519,20 b' def getrepocaps(repo, allowpushback=Fals'
         caps['checkheads'] = ('related',)
     if 'phases' in repo.ui.configlist('devel', 'legacy.exchange'):
         caps.pop('phases')
-    if not repo.ui.configbool('experimental', 'bundle2.stream'):
-        caps.pop('stream')
+
+    # Don't advertise stream clone support in server mode if not configured.
+    if role == 'server':
+        streamsupported = repo.ui.configbool('server', 'uncompressed',
+                                             untrusted=True)
+        featuresupported = repo.ui.configbool('experimental', 'bundle2.stream')
+
+        if not streamsupported or not featuresupported:
+            caps.pop('stream')
+    # role == 'client'
+    else:
+        if not repo.ui.configbool('experimental', 'bundle2.stream'):
+            caps.pop('stream')
+
     return caps
 
 def bundle2caps(remote):

tests/test-clone-uncompressed.t

@@ -102,7 +102,7 b' Cannot stream clone when server.uncompre'
   Main capabilities:
     batch
     branchmap
-    $USUAL_BUNDLE2_CAPS$%0Astream%3Dv2
+    $USUAL_BUNDLE2_CAPS$
     changegroupsubset
     compression=zstd,zlib
     getbundle
@@ -136,8 +136,6 b' Cannot stream clone when server.uncompre'
     remote-changegroup
       http
       https
-    stream
-      v2
 
   $ hg clone --stream -U http://localhost:$HGPORT server-disabled
   warning: stream clone requested but server has them disabled