narrow: check for servers' narrow support before doing anything (BC)

Recently we introduced narrow capabilities for the server. So we can check
whether a server has narrow clone support or not before doing anything. This is
BC because new clients won't be able to extend from old narrow-enabled servers.
I *think* narrow is not used much (maybe just inside Google), also it's
experimental so I think we can change this. We will need to this someday anyway.

The "doesn't" in error is changed to "does not" because I think that's we do in
core. I also changed one more instance of the error message to use 'does not'
for consistency.

Differential Revision: https://phab.mercurial-scm.org/D4789

hgext/narrow/narrowcommands.py

@@ -134,7 +134,7 b' def pullbundle2extraprepare(orig, pullop'
         return orig(pullop, kwargs)
 
     if wireprotoserver.NARROWCAP not in pullop.remote.capabilities():
-        raise error.Abort(_("server doesn't support narrow clones"))
+        raise error.Abort(_("server does not support narrow clones"))
     orig(pullop, kwargs)
     kwargs['narrow'] = True
     include, exclude = repo.narrowpats
@@ -408,6 +408,13 b' def trackedcmd(ui, repo, remotepath=None'
         url, branches = hg.parseurl(remotepath)
         ui.status(_('comparing with %s\n') % util.hidepassword(url))
         remote = hg.peer(repo, opts, url)
+
+        # check narrow support before doing anything if widening needs to be
+        # performed. In future we should also abort if client is ellipses and
+        # server does not support ellipses
+        if widening and wireprotoserver.NARROWCAP not in remote.capabilities():
+            raise error.Abort(_("server does not support narrow clones"))
+
         commoninc = discovery.findcommonincoming(repo, remote)
 
         oldincludes, oldexcludes = repo.narrowpats

tests/test-narrow-clone-non-narrow-server.t

@@ -39,7 +39,7 b' Verify that narrow is advertised in the '
 
   $ hg clone --narrow --include f1 http://localhost:$HGPORT1/ narrowclone
   requesting all changes
-  abort: server doesn't support narrow clones
+  abort: server does not support narrow clones
   [255]
 
 Make a narrow clone (via HGPORT2), then try to narrow and widen
@@ -60,7 +60,5 b' gracefully:'
   looking for local changes to affected paths
   $ hg tracked --addinclude f1 http://localhost:$HGPORT1/
   comparing with http://localhost:$HGPORT1/
-  searching for changes
-  no changes found
-  abort: server doesn't support narrow clones
+  abort: server does not support narrow clones
   [255]

tests/test-narrow-clone.t

@@ -65,7 +65,7 b' BUG: local-to-local narrow clones should'
 
   $ hg clone --narrow master narrow-via-localpeer --noupdate --include "dir/src/f10"
   requesting all changes
-  abort: server doesn't support narrow clones
+  abort: server does not support narrow clones
   [255]
   $ hg tracked -R narrow-via-localpeer
   abort: repository narrow-via-localpeer not found!