diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -829,6 +829,7 @@ def debugdiscovery(ui, repo, remoteurl="
data['nb-common'] = len(common)
data['nb-common-local'] = len(common & lheads)
data['nb-common-remote'] = len(common & rheads)
+ data['nb-common-both'] = len(common & rheads & lheads)
data['nb-local'] = len(lheads)
data['nb-local-missing'] = data['nb-local'] - data['nb-common-local']
data['nb-remote'] = len(rheads)
@@ -843,6 +844,7 @@ def debugdiscovery(ui, repo, remoteurl="
ui.write((" total common heads: %(nb-common)9d\n") % data)
ui.write((" also local heads: %(nb-common-local)9d\n") % data)
ui.write((" also remote heads: %(nb-common-remote)9d\n") % data)
+ ui.write((" both: %(nb-common-both)9d\n") % data)
ui.write((" local heads: %(nb-local)9d\n") % data)
ui.write((" common: %(nb-common-local)9d\n") % data)
ui.write((" missing: %(nb-local-missing)9d\n") % data)
diff --git a/tests/test-setdiscovery.t b/tests/test-setdiscovery.t
--- a/tests/test-setdiscovery.t
+++ b/tests/test-setdiscovery.t
@@ -48,6 +48,7 @@ Small superset:
total common heads: 2
also local heads: 2
also remote heads: 1
+ both: 1
local heads: 2
common: 2
missing: 0
@@ -69,6 +70,7 @@ Small superset:
total common heads: 2
also local heads: 2
also remote heads: 1
+ both: 1
local heads: 2
common: 2
missing: 0
@@ -90,6 +92,7 @@ Small superset:
total common heads: 1
also local heads: 1
also remote heads: 0
+ both: 0
local heads: 2
common: 1
missing: 1
@@ -110,6 +113,7 @@ Small superset:
total common heads: 2
also local heads: 1
also remote heads: 2
+ both: 1
local heads: 3
common: 1
missing: 2
@@ -131,6 +135,7 @@ Small superset:
total common heads: 2
also local heads: 1
also remote heads: 2
+ both: 1
local heads: 3
common: 1
missing: 2
@@ -152,6 +157,7 @@ Small superset:
total common heads: 2
also local heads: 1
also remote heads: 2
+ both: 1
local heads: 3
common: 1
missing: 2
@@ -179,6 +185,7 @@ Many new:
total common heads: 1
also local heads: 1
also remote heads: 0
+ both: 0
local heads: 2
common: 1
missing: 1
@@ -203,6 +210,7 @@ Many new:
total common heads: 1
also local heads: 1
also remote heads: 0
+ both: 0
local heads: 2
common: 1
missing: 1
@@ -227,6 +235,7 @@ Many new:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 2
common: 0
missing: 2
@@ -247,6 +256,7 @@ Many new:
total common heads: 1
also local heads: 0
also remote heads: 1
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -271,6 +281,7 @@ Many new:
total common heads: 1
also local heads: 0
also remote heads: 1
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -295,6 +306,7 @@ Many new:
total common heads: 1
also local heads: 0
also remote heads: 1
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -321,6 +333,7 @@ Both sides many new with stub:
total common heads: 1
also local heads: 1
also remote heads: 0
+ both: 0
local heads: 2
common: 1
missing: 1
@@ -345,6 +358,7 @@ Both sides many new with stub:
total common heads: 1
also local heads: 1
also remote heads: 0
+ both: 0
local heads: 2
common: 1
missing: 1
@@ -369,6 +383,7 @@ Both sides many new with stub:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 2
common: 0
missing: 2
@@ -389,6 +404,7 @@ Both sides many new with stub:
total common heads: 1
also local heads: 0
also remote heads: 1
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -413,6 +429,7 @@ Both sides many new with stub:
total common heads: 1
also local heads: 0
also remote heads: 1
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -437,6 +454,7 @@ Both sides many new with stub:
total common heads: 1
also local heads: 0
also remote heads: 1
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -464,6 +482,7 @@ Both many new:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -488,6 +507,7 @@ Both many new:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -512,6 +532,7 @@ Both many new:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -532,6 +553,7 @@ Both many new:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -556,6 +578,7 @@ Both many new:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -580,6 +603,7 @@ Both many new:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -607,6 +631,7 @@ Both many new skewed:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -631,6 +656,7 @@ Both many new skewed:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -655,6 +681,7 @@ Both many new skewed:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -675,6 +702,7 @@ Both many new skewed:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -699,6 +727,7 @@ Both many new skewed:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -723,6 +752,7 @@ Both many new skewed:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -750,6 +780,7 @@ Both many new on top of long history:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -777,6 +808,7 @@ Both many new on top of long history:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -804,6 +836,7 @@ Both many new on top of long history:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -824,6 +857,7 @@ Both many new on top of long history:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -851,6 +885,7 @@ Both many new on top of long history:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -878,6 +913,7 @@ Both many new on top of long history:
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 1
common: 0
missing: 1
@@ -957,6 +993,7 @@ One with >200 heads, which used to use u
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 260
common: 0
missing: 260
@@ -983,6 +1020,7 @@ One with >200 heads, which used to use u
total common heads: 1
also local heads: 0
also remote heads: 0
+ both: 0
local heads: 260
common: 0
missing: 260