diff --git a/mercurial/bundle2.py b/mercurial/bundle2.py
index 64dd8f25fcf43b189c53deec943687d5c19d5999_bWVyY3VyaWFsL2J1bmRsZTIucHk=..c3ef4f3b868043e4131692a48bb76dafbad9761d_bWVyY3VyaWFsL2J1bmRsZTIucHk= 100644
--- a/mercurial/bundle2.py
+++ b/mercurial/bundle2.py
@@ -179,7 +179,7 @@
 
 def indebug(ui, message):
     """debug on input stream (unbundling)"""
-    ui.debug(message)
+    ui.debug('bundle2-input: %s' % message)
 
 def validateparttype(parttype):
     """raise ValueError if a parttype contains invalid character"""
diff --git a/tests/test-bundle2-format.t b/tests/test-bundle2-format.t
index 64dd8f25fcf43b189c53deec943687d5c19d5999_dGVzdHMvdGVzdC1idW5kbGUyLWZvcm1hdC50..c3ef4f3b868043e4131692a48bb76dafbad9761d_dGVzdHMvdGVzdC1idW5kbGUyLWZvcm1hdC50 100644
--- a/tests/test-bundle2-format.t
+++ b/tests/test-bundle2-format.t
@@ -350,11 +350,11 @@
 unbundling debug
 
   $ hg statbundle2 --debug --config progress.debug=true < ../out.hg2
-  start processing of HG20 stream
-  reading bundle2 stream parameters
-  ignoring unknown parameter 'e|! 7/'
-  ignoring unknown parameter 'simple'
+  bundle2-input: start processing of HG20 stream
+  bundle2-input: reading bundle2 stream parameters
+  bundle2-input: ignoring unknown parameter 'e|! 7/'
+  bundle2-input: ignoring unknown parameter 'simple'
   options count: 2
   - e|! 7/
       babar%#==tutu
   - simple
@@ -357,10 +357,10 @@
   options count: 2
   - e|! 7/
       babar%#==tutu
   - simple
-  start extraction of bundle2 parts
-  part header size: 0
-  end of bundle2 stream
+  bundle2-input: start extraction of bundle2 parts
+  bundle2-input: part header size: 0
+  bundle2-input: end of bundle2 stream
   parts count:   0
 
 
@@ -437,6 +437,6 @@
   parts count:   7
 
   $ hg statbundle2 --debug --config progress.debug=true < ../parts.hg2
-  start processing of HG20 stream
-  reading bundle2 stream parameters
+  bundle2-input: start processing of HG20 stream
+  bundle2-input: reading bundle2 stream parameters
   options count: 0
@@ -442,9 +442,9 @@
   options count: 0
-  start extraction of bundle2 parts
-  part header size: 17
-  part type: "test:empty"
-  part id: "0"
-  part parameters: 0
+  bundle2-input: start extraction of bundle2 parts
+  bundle2-input: part header size: 17
+  bundle2-input: part type: "test:empty"
+  bundle2-input: part id: "0"
+  bundle2-input: part parameters: 0
     :test:empty:
       mandatory: 0
       advisory: 0
@@ -448,5 +448,5 @@
     :test:empty:
       mandatory: 0
       advisory: 0
-  payload chunk size: 0
+  bundle2-input: payload chunk size: 0
       payload: 0 bytes
@@ -452,8 +452,8 @@
       payload: 0 bytes
-  part header size: 17
-  part type: "test:empty"
-  part id: "1"
-  part parameters: 0
+  bundle2-input: part header size: 17
+  bundle2-input: part type: "test:empty"
+  bundle2-input: part id: "1"
+  bundle2-input: part parameters: 0
     :test:empty:
       mandatory: 0
       advisory: 0
@@ -457,5 +457,5 @@
     :test:empty:
       mandatory: 0
       advisory: 0
-  payload chunk size: 0
+  bundle2-input: payload chunk size: 0
       payload: 0 bytes
@@ -461,8 +461,8 @@
       payload: 0 bytes
-  part header size: 16
-  part type: "test:song"
-  part id: "2"
-  part parameters: 0
+  bundle2-input: part header size: 16
+  bundle2-input: part type: "test:song"
+  bundle2-input: part id: "2"
+  bundle2-input: part parameters: 0
     :test:song:
       mandatory: 0
       advisory: 0
@@ -466,6 +466,6 @@
     :test:song:
       mandatory: 0
       advisory: 0
-  payload chunk size: 178
-  payload chunk size: 0
+  bundle2-input: payload chunk size: 178
+  bundle2-input: payload chunk size: 0
       payload: 178 bytes
@@ -471,8 +471,8 @@
       payload: 178 bytes
-  part header size: 22
-  part type: "test:debugreply"
-  part id: "3"
-  part parameters: 0
+  bundle2-input: part header size: 22
+  bundle2-input: part type: "test:debugreply"
+  bundle2-input: part id: "3"
+  bundle2-input: part parameters: 0
     :test:debugreply:
       mandatory: 0
       advisory: 0
@@ -476,5 +476,5 @@
     :test:debugreply:
       mandatory: 0
       advisory: 0
-  payload chunk size: 0
+  bundle2-input: payload chunk size: 0
       payload: 0 bytes
@@ -480,8 +480,8 @@
       payload: 0 bytes
-  part header size: 43
-  part type: "test:math"
-  part id: "4"
-  part parameters: 3
+  bundle2-input: part header size: 43
+  bundle2-input: part type: "test:math"
+  bundle2-input: part id: "4"
+  bundle2-input: part parameters: 3
     :test:math:
       mandatory: 2
       advisory: 1
@@ -485,6 +485,6 @@
     :test:math:
       mandatory: 2
       advisory: 1
-  payload chunk size: 2
-  payload chunk size: 0
+  bundle2-input: payload chunk size: 2
+  bundle2-input: payload chunk size: 0
       payload: 2 bytes
@@ -490,8 +490,8 @@
       payload: 2 bytes
-  part header size: 29
-  part type: "test:song"
-  part id: "5"
-  part parameters: 1
+  bundle2-input: part header size: 29
+  bundle2-input: part type: "test:song"
+  bundle2-input: part id: "5"
+  bundle2-input: part parameters: 1
     :test:song:
       mandatory: 1
       advisory: 0
@@ -495,5 +495,5 @@
     :test:song:
       mandatory: 1
       advisory: 0
-  payload chunk size: 0
+  bundle2-input: payload chunk size: 0
       payload: 0 bytes
@@ -499,8 +499,8 @@
       payload: 0 bytes
-  part header size: 16
-  part type: "test:ping"
-  part id: "6"
-  part parameters: 0
+  bundle2-input: part header size: 16
+  bundle2-input: part type: "test:ping"
+  bundle2-input: part id: "6"
+  bundle2-input: part parameters: 0
     :test:ping:
       mandatory: 0
       advisory: 0
@@ -504,5 +504,5 @@
     :test:ping:
       mandatory: 0
       advisory: 0
-  payload chunk size: 0
+  bundle2-input: payload chunk size: 0
       payload: 0 bytes
@@ -508,6 +508,6 @@
       payload: 0 bytes
-  part header size: 0
-  end of bundle2 stream
+  bundle2-input: part header size: 0
+  bundle2-input: end of bundle2 stream
   parts count:   7
 
 Test actual unbundling of test part
@@ -516,24 +516,24 @@
 Process the bundle
 
   $ hg unbundle2 --debug --config progress.debug=true < ../parts.hg2
-  start processing of HG20 stream
-  reading bundle2 stream parameters
-  start extraction of bundle2 parts
-  part header size: 17
-  part type: "test:empty"
-  part id: "0"
-  part parameters: 0
-  ignoring unsupported advisory part test:empty
-  payload chunk size: 0
-  part header size: 17
-  part type: "test:empty"
-  part id: "1"
-  part parameters: 0
-  ignoring unsupported advisory part test:empty
-  payload chunk size: 0
-  part header size: 16
-  part type: "test:song"
-  part id: "2"
-  part parameters: 0
-  found a handler for part 'test:song'
+  bundle2-input: start processing of HG20 stream
+  bundle2-input: reading bundle2 stream parameters
+  bundle2-input: start extraction of bundle2 parts
+  bundle2-input: part header size: 17
+  bundle2-input: part type: "test:empty"
+  bundle2-input: part id: "0"
+  bundle2-input: part parameters: 0
+  bundle2-input: ignoring unsupported advisory part test:empty
+  bundle2-input: payload chunk size: 0
+  bundle2-input: part header size: 17
+  bundle2-input: part type: "test:empty"
+  bundle2-input: part id: "1"
+  bundle2-input: part parameters: 0
+  bundle2-input: ignoring unsupported advisory part test:empty
+  bundle2-input: payload chunk size: 0
+  bundle2-input: part header size: 16
+  bundle2-input: part type: "test:song"
+  bundle2-input: part id: "2"
+  bundle2-input: part parameters: 0
+  bundle2-input: found a handler for part 'test:song'
   The choir starts singing:
@@ -539,6 +539,6 @@
   The choir starts singing:
-  payload chunk size: 178
-  payload chunk size: 0
+  bundle2-input: payload chunk size: 178
+  bundle2-input: payload chunk size: 0
       Patali Dirapata, Cromda Cromda Ripalo, Pata Pata, Ko Ko Ko
       Bokoro Dipoulito, Rondi Rondi Pepino, Pata Pata, Ko Ko Ko
       Emana Karassoli, Loucra Loucra Ponponto, Pata Pata, Ko Ko Ko.
@@ -542,9 +542,9 @@
       Patali Dirapata, Cromda Cromda Ripalo, Pata Pata, Ko Ko Ko
       Bokoro Dipoulito, Rondi Rondi Pepino, Pata Pata, Ko Ko Ko
       Emana Karassoli, Loucra Loucra Ponponto, Pata Pata, Ko Ko Ko.
-  part header size: 22
-  part type: "test:debugreply"
-  part id: "3"
-  part parameters: 0
-  found a handler for part 'test:debugreply'
+  bundle2-input: part header size: 22
+  bundle2-input: part type: "test:debugreply"
+  bundle2-input: part id: "3"
+  bundle2-input: part parameters: 0
+  bundle2-input: found a handler for part 'test:debugreply'
   debugreply: no reply
@@ -550,22 +550,22 @@
   debugreply: no reply
-  payload chunk size: 0
-  part header size: 43
-  part type: "test:math"
-  part id: "4"
-  part parameters: 3
-  ignoring unsupported advisory part test:math
-  payload chunk size: 2
-  payload chunk size: 0
-  part header size: 29
-  part type: "test:song"
-  part id: "5"
-  part parameters: 1
-  found a handler for part 'test:song'
-  ignoring unsupported advisory part test:song - randomparam
-  payload chunk size: 0
-  part header size: 16
-  part type: "test:ping"
-  part id: "6"
-  part parameters: 0
-  found a handler for part 'test:ping'
+  bundle2-input: payload chunk size: 0
+  bundle2-input: part header size: 43
+  bundle2-input: part type: "test:math"
+  bundle2-input: part id: "4"
+  bundle2-input: part parameters: 3
+  bundle2-input: ignoring unsupported advisory part test:math
+  bundle2-input: payload chunk size: 2
+  bundle2-input: payload chunk size: 0
+  bundle2-input: part header size: 29
+  bundle2-input: part type: "test:song"
+  bundle2-input: part id: "5"
+  bundle2-input: part parameters: 1
+  bundle2-input: found a handler for part 'test:song'
+  bundle2-input: ignoring unsupported advisory part test:song - randomparam
+  bundle2-input: payload chunk size: 0
+  bundle2-input: part header size: 16
+  bundle2-input: part type: "test:ping"
+  bundle2-input: part id: "6"
+  bundle2-input: part parameters: 0
+  bundle2-input: found a handler for part 'test:ping'
   received ping request (id 6)
@@ -571,7 +571,7 @@
   received ping request (id 6)
-  payload chunk size: 0
-  part header size: 0
-  end of bundle2 stream
+  bundle2-input: payload chunk size: 0
+  bundle2-input: part header size: 0
+  bundle2-input: end of bundle2 stream
   0 unread bytes
   3 total verses sung