bundle2: allow compression options to be passed to compressor

Compression engines allow options to be passed to them to control
behavior. This patch exposes an argument to bundle2.writebundle()
that passes options to the compression engine when writing compressed
bundles. The argument is honored for both bundle1 and bundle2, the
latter requiring a bit of plumbing to pass the value around.

mercurial/bundle2.py

@@ -512,14 +512,16 b' class bundle20(object):'
         self._parts = []
         self.capabilities = dict(capabilities)
         self._compengine = util.compengines.forbundletype('UN')
+        self._compopts = None
 
-    def setcompression(self, alg):
+    def setcompression(self, alg, compopts=None):
         """setup core part compression to <alg>"""
         if alg in (None, 'UN'):
             return
         assert not any(n.lower() == 'Compression' for n, v in self._params)
         self.addparam('Compression', alg)
         self._compengine = util.compengines.forbundletype(alg)
+        self._compopts = compopts
 
     @property
     def nbparts(self):
@@ -571,7 +573,8 b' class bundle20(object):'
         yield _pack(_fstreamparamsize, len(param))
         if param:
             yield param
-        for chunk in self._compengine.compressstream(self._getcorechunk()):
+        for chunk in self._compengine.compressstream(self._getcorechunk(),
+                                                     self._compopts):
             yield chunk
 
     def _paramchunk(self):
@@ -1289,7 +1292,8 b' def obsmarkersversion(caps):'
     obscaps = caps.get('obsmarkers', ())
     return [int(c[1:]) for c in obscaps if c.startswith('V')]
 
-def writebundle(ui, cg, filename, bundletype, vfs=None, compression=None):
+def writebundle(ui, cg, filename, bundletype, vfs=None, compression=None,
+                compopts=None):
     """Write a bundle file and return its filename.
 
     Existing files will not be overwritten.
@@ -1300,7 +1304,7 b' def writebundle(ui, cg, filename, bundle'
 
     if bundletype == "HG20":
         bundle = bundle20(ui)
-        bundle.setcompression(compression)
+        bundle.setcompression(compression, compopts)
         part = bundle.newpart('changegroup', data=cg.getchunks())
         part.addparam('version', cg.version)
         if 'clcount' in cg.extras:
@@ -1320,7 +1324,7 b' def writebundle(ui, cg, filename, bundle'
         compengine = util.compengines.forbundletype(comp)
         def chunkiter():
             yield header
-            for chunk in compengine.compressstream(cg.getchunks()):
+            for chunk in compengine.compressstream(cg.getchunks(), compopts):
                 yield chunk
         chunkiter = chunkiter()