verify that received files have the correct size

Summary:
Streaming clone implementation did not check that received files have the corrects. This change addresses it.

Before this change if connection was interrupted for whatever reason client would treat fetch of changeset as successful and proceed with cloning operations, but later checks would report corruption of internal state of hg data. This is based on user [report](https://fb.workplace.com/groups/scm/permalink/3177150312334567/)

Reviewed By: quark-zju, krallin

Differential Revision: D23572058

fbshipit-source-id: d740b45ca217cd6db0a65e01aabc2ba9a4835221

eden/scm/edenscm/mercurial/streamclone.py

@@ -374,9 +374,17 @@ def consumev1(repo, fp, filecount, bytecount):
                         # for backwards compat, name was partially encoded
                         path = store.decodedir(decodeutf8(name))
                         with repo.svfs(path, "w", backgroundclose=True) as ofp:
+                            fetchedsize = 0
                             for chunk in util.filechunkiter(fp, limit=size):
-                                prog.value += len(chunk)
                                 ofp.write(chunk)
+                                chunksize = len(chunk)
+                                prog.value += chunksize
+                                fetchedsize += chunksize
+                            if fetchedsize != size:
+                                msg = _(
+                                    "failed to fully fetch %s: fetched:%s expected:%s"
+                                ) % (name, fetchedsize, size)
+                                raise error.Abort(msg)
 
                 # force @filecache properties to be reloaded from
                 # streamclone-ed file at next access