wireproto: allow unbundle with hashed heads parameter (issue2126)

Current wire protocol of unbundle sends the list of all heads in the remote
repository to avoid race condition.  This causes "URL too long" error on HTTP
server when the repository has many heads.

This change allows clients to send SHA1 hash of sorted head hashes instead.
Also, this introduces "unbundlehash" capability to inform them that the server
accepts hashed heads parameter.

tests/test-unbundlehash.t

@@ -0,0 +1,31 b''
+
+Test wire protocol unbundle with hashed heads (capability: unbundlehash)
+
+Create a remote repository.
+
+  $ hg init remote
+  $ hg serve -R remote --config web.push_ssl=False --config web.allow_push=* -p $HGPORT -d --pid-file=hg1.pid -E error.log -A access.log
+  $ cat hg1.pid >> $DAEMON_PIDS
+
+Clone the repository and push a change.
+
+  $ hg clone http://localhost:$HGPORT/ local
+  no changes found
+  updating to branch default
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ touch local/README
+  $ hg ci -R local -A -m hoge
+  adding README
+  $ hg push -R local
+  pushing to http://localhost:$HGPORT/
+  searching for changes
+  remote: adding changesets
+  remote: adding manifests
+  remote: adding file changes
+  remote: added 1 changesets with 1 changes to 1 files
+
+Ensure hashed heads format is used.
+The hash here is always the same since the remote repository only has the null head.
+
+  $ cat access.log | grep unbundle
+  * - - [*] "POST /?cmd=unbundle&heads=686173686564+6768033e216468247bd031a0a2d9876d79818f8f HTTP/1.1" 200 - (glob)

mercurial/wireproto.py

@@ -139,7 +139,13 b' class wirerepository(repo.repository):'
         remote server as a bundle. Return an integer indicating the
         result of the push (see localrepository.addchangegroup()).'''
 
-        ret, output = self._callpush("unbundle", cg, heads=encodelist(heads))
+        if self.capable('unbundlehash'):
+            heads = encodelist(['hashed',
+                                util.sha1(''.join(sorted(heads))).digest()])
+        else:
+            heads = encodelist(heads)
+
+        ret, output = self._callpush("unbundle", cg, heads=heads)
         if ret == "":
             raise error.ResponseError(
                 _('push failed:'), output)
@@ -216,7 +222,8 b' def branches(repo, proto, nodes):'
     return "".join(r)
 
 def capabilities(repo, proto):
-    caps = 'lookup changegroupsubset branchmap pushkey known getbundle'.split()
+    caps = ('lookup changegroupsubset branchmap pushkey known getbundle '
+            'unbundlehash').split()
     if _allowstream(repo.ui):
         requiredformats = repo.requirements & repo.supportedformats
         # if our local revlogs are just revlogv1, add 'stream' cap
@@ -353,7 +360,9 b' def unbundle(repo, proto, heads):'
 
     def check_heads():
         heads = repo.heads()
-        return their_heads == ['force'] or their_heads == heads
+        heads_hash = util.sha1(''.join(sorted(heads))).digest()
+        return (their_heads == ['force'] or their_heads == heads or
+                their_heads == ['hashed', heads_hash])
 
     proto.redirect()
 

tests/test-hgweb-commands.t

@@ -943,7 +943,7 b' capabilities'
   $ "$TESTDIR/get-with-headers.py" 127.0.0.1:$HGPORT '?cmd=capabilities'; echo
   200 Script output follows
   
-  lookup changegroupsubset branchmap pushkey known getbundle unbundle=HG10GZ,HG10BZ,HG10UN
+  lookup changegroupsubset branchmap pushkey known getbundle unbundlehash unbundle=HG10GZ,HG10BZ,HG10UN
 
 heads