--- a/mercurial/commands.py	Thu Jan 14 21:27:53 2016 -0800
+++ b/mercurial/commands.py	Thu Jan 14 22:57:55 2016 -0800
@@ -2007,12 +2007,18 @@
         release(tr, lock)
 
 @command('debugbundle',
-        [('a', 'all', None, _('show all details'))],
+        [('a', 'all', None, _('show all details')),
+         ('', 'spec', None, _('print the bundlespec of the bundle'))],
         _('FILE'),
         norepo=True)
-def debugbundle(ui, bundlepath, all=None, **opts):
+def debugbundle(ui, bundlepath, all=None, spec=None, **opts):
     """lists the contents of a bundle"""
     with hg.openpath(ui, bundlepath) as f:
+        if spec:
+            spec = exchange.getbundlespec(ui, f)
+            ui.write('%s\n' % spec)
+            return
+
         gen = exchange.readbundle(ui, f, bundlepath)
         if isinstance(gen, bundle2.unbundle20):
             return _debugbundle2(ui, gen, all=all, **opts)

--- a/tests/test-bundle-type.t	Thu Jan 14 21:27:53 2016 -0800
+++ b/tests/test-bundle-type.t	Thu Jan 14 22:57:55 2016 -0800
@@ -43,6 +43,7 @@
   >   f -q -B6 -D ../b$t; echo
   >   cd ../t$t
   >   hg debugbundle ../b$t
+  >   hg debugbundle --spec ../b$t
   >   echo
   >   cd ..
   > done
@@ -53,6 +54,7 @@
   Stream params: {}
   changegroup -- "{'version': '02'}"
       c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
+  none-v2
   
   % test bundle type bzip2
   searching for changes
@@ -61,6 +63,7 @@
   Stream params: {'Compression': 'BZ'}
   changegroup -- "{'version': '02'}"
       c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
+  bzip2-v2
   
   % test bundle type gzip
   searching for changes
@@ -69,6 +72,7 @@
   Stream params: {'Compression': 'GZ'}
   changegroup -- "{'version': '02'}"
       c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
+  gzip-v2
   
   % test bundle type none-v2
   searching for changes
@@ -77,6 +81,7 @@
   Stream params: {}
   changegroup -- "{'version': '02'}"
       c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
+  none-v2
   
   % test bundle type v2
   searching for changes
@@ -85,18 +90,21 @@
   Stream params: {'Compression': 'BZ'}
   changegroup -- "{'version': '02'}"
       c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
+  bzip2-v2
   
   % test bundle type v1
   searching for changes
   1 changesets found
   HG10BZ
   c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
+  bzip2-v1
   
   % test bundle type gzip-v1
   searching for changes
   1 changesets found
   HG10GZ
   c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
+  gzip-v1
   
 
 test garbage file

--- a/tests/test-bundle.t	Thu Jan 14 21:27:53 2016 -0800
+++ b/tests/test-bundle.t	Thu Jan 14 22:57:55 2016 -0800
@@ -276,6 +276,9 @@
   0020: 65 6c 74 61 2c 72 65 76 6c 6f 67 76 31 00 64 61 |elta,revlogv1.da|
   0030: 74 61 2f 61 64 69 66 66 65 72 65 6e 74 66 69 6c |ta/adifferentfil|
 
+  $ hg debugbundle --spec packed.hg
+  none-packed1;requirements%3Dgeneraldelta%2Crevlogv1
+
 generaldelta requirement is listed in stream clone bundles
 
   $ hg --config format.generaldelta=true init testgd
@@ -294,6 +297,9 @@
   0020: 65 6c 74 61 2c 72 65 76 6c 6f 67 76 31 00 64 61 |elta,revlogv1.da|
   0030: 74 61 2f 66 6f 6f 2e 69 00 36 34 0a 00 03 00 01 |ta/foo.i.64.....|
 
+  $ hg debugbundle --spec packedgd.hg
+  none-packed1;requirements%3Dgeneraldelta%2Crevlogv1
+
 Unpacking packed1 bundles with "hg unbundle" isn't allowed
 
   $ hg init packed

--- a/tests/test-completion.t	Thu Jan 14 21:27:53 2016 -0800
+++ b/tests/test-completion.t	Thu Jan 14 22:57:55 2016 -0800
@@ -236,7 +236,7 @@
   debugancestor: 
   debugapplystreamclonebundle: 
   debugbuilddag: mergeable-file, overwritten-file, new-file
-  debugbundle: all
+  debugbundle: all, spec
   debugcheckstate: 
   debugcommands: 
   debugcomplete: options