git-p4: add file streaming progress in verbose mode

If a file is streamed from P4 to Git then the verbose mode prints
continuously the progress as percentage like this:
//depot/file.bin 20% (10 MB)

Upon completion the progress is overwritten with depot source, local
file and size like this:
//depot/file.bin --> local/file.bin (10 MB)

Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-p4.py

@@ -2171,7 +2171,9 @@ def splitFilesIntoBranches(self, commit):
     def streamOneP4File(self, file, contents):
         relPath = self.stripRepoPath(file['depotFile'], self.branchPrefixes)
         if verbose:
-            sys.stderr.write("%s\n" % relPath)
+            size = int(self.stream_file['fileSize'])
+            sys.stdout.write('\r%s --> %s (%i MB)\n' % (file['depotFile'], relPath, size/1024/1024))
+            sys.stdout.flush()
 
         (type_base, type_mods) = split_p4_type(file["type"])
 
@@ -2248,7 +2250,8 @@ def streamOneP4File(self, file, contents):
     def streamOneP4Deletion(self, file):
         relPath = self.stripRepoPath(file['path'], self.branchPrefixes)
         if verbose:
-            sys.stderr.write("delete %s\n" % relPath)
+            sys.stdout.write("delete %s\n" % relPath)
+            sys.stdout.flush()
         self.gitStream.write("D %s\n" % relPath)
 
     # handle another chunk of streaming data
@@ -2288,10 +2291,23 @@ def streamP4FilesCb(self, marshalled):
         # 'data' field we need to append to our array
         for k in marshalled.keys():
             if k == 'data':
+                if 'streamContentSize' not in self.stream_file:
+                    self.stream_file['streamContentSize'] = 0
+                self.stream_file['streamContentSize'] += len(marshalled['data'])
                 self.stream_contents.append(marshalled['data'])
             else:
                 self.stream_file[k] = marshalled[k]
 
+        if (verbose and
+            'streamContentSize' in self.stream_file and
+            'fileSize' in self.stream_file and
+            'depotFile' in self.stream_file):
+            size = int(self.stream_file["fileSize"])
+            if size > 0:
+                progress = 100*self.stream_file['streamContentSize']/size
+                sys.stdout.write('\r%s %d%% (%i MB)' % (self.stream_file['depotFile'], progress, int(size/1024/1024)))
+                sys.stdout.flush()
+
         self.stream_have_file_info = True
 
     # Stream directly from "p4 files" into "git fast-import"